The Vuelta a Espana may have a reputation as a revenge race for riders who missed out in the Tour de France but there won't be much redemption in the air ar this year's Spanish grand tour. Instead, the race has attracted a formidable line-up of grand tour stars who travel to Spain on the back of what has mostly been highly successful seasons. Giro champion Vincenzo Nibali (Astana) and local heroes Joaquim Rodriguez (Katusha) and Alejandro Valverde (Movistar) have attracted most pre-race interest but they will have to contend with exciting talents Sergio Henao (Sky), Carlos Betancur (Ag2r), Rigoberto Uran (Sky), Thibaut Pinot (FDJ) and Rafal Majka (Saxo-Tinkoff) and accomplished grand tour veterans Michele Scarponi (Lampre), Ivan Basso (Cannondale) and Samuel Sanchez (Euskaltel). Defending champion Alberto Contador and the best two riders from the Tour de France may be absent but apart from that Vuelta organizers Unipublic could hardly have imagined a stronger line-up for their race. CyclingQuotes.com takes a thorough look at this year's favourites and outsiders and finds out all about their strengths and weaknesses.

Last year's Vuelta a Espana evolved into a local battle between the three Spanish grand tour giants Alberto Contador, Joaquim Rodriguez and Alejandro Valverde but this year's race should have a much more international flavour. Valverde and Rodriguez are back after having impressed in the Tour de France but those two join Samuel Sanchez on the list as the only genuine Spanish winner candidates.

Italy's three grand tour winners Vincenzo Nibali, Ivan Basso and Michele Scarponi have all made the Vuelta a prime target and a host of exciting Colombian talents are ready to continue their recent domination. On a course that offers no less than 11 uphill finishes, such a bunch of climbers can only create a very exciting bike race and the race could very well shape up to be the closest of this year's grand tours.

CyclingQuotes.com has taken an in-depth look at the race's favourites, assigning 5 stars to the race's biggest favourite, 4 to his two biggest rivals, 3 to three other potential winners, 2 to four of the podium contenders and 1 to 5 of the race's minor outsiders. In this article, we take a look at the 4-star riders that may be seen as the main challengers to the race's biggest favourite.

Sergio Henao (****)

Sergio Henao may never have finished on a grand tour podium but don't be fooled by his palmares. Anyone who has followed his progress during his first time as a professional road racer will know that this kid has what it takes to win a grand tour.

Much of the recent interest in Colombian cycling has mainly been focused on Nairo Quintana and to a lesser extent Carlos Betancur and Rigoberto Uran. Henao has flown a bit more under the radar but based on his previous performances, there's no reason that Henao cannot go on to match his Movistar compatriot as a grand tour rider.

The 25-year old was given a surprisingly late chance in the European peloton when he was signed by Sky on the back of a queen stage win in the Tour of Utah in 2011. It's no mean feat to be picked up by the British super team and it's testament to his talent that the Brits singled him out as their man for the future.

He showed his potential from the beginning by finishing 3rd in the hardest of the Mallorca races before going on to finish 3rd on a extremely steep finishing climb in the Vuelta al Pais Vasco. He did a good ride at his maiden grand tour at the Giro when he made it into the top 10 in his first attempt but as it is often seen- Quintana is just another example - young riders take a further step up when they have completed their first three-week race. That was certainly the case for Henao who returned to racing in the Tour of Poland later that summer and emerged as the strongest climber in the race. The course was not selective enough and so he had to settle for 3rd before going on to leave the world elite behind when he joined forces with Johan Esteban Chaves in the queen stage of the Vuelta a Burgos .He worked as a domestique for Froome at the Vuelta but proved his recovery abilities and consistency when he kept going strong all the way to the end of the season, finishing 9th in the world championships, 4th in Gran Piemonte and 5th in Il Lombardia.

This year he had added another level to his climbing when he crushed the opposition on the Volta ao Algarve queen stage but his real standout performance came at the Vuelta al Pais Vasco. He was the strongest climber in that race - stronger than Quintana, Richie Porte and Alberto Contador - but lost the leader's jersey in the final time trial. He finished 6th in the Amstel Gold Race and an amazing 2nd in the Fleche Wallonne but paid for a heavy racing schedule in the Giro where he was a disappointing 16th.

Having learnt from that mistake, he has limited his racing prior to his big season objective. Since the Giro, he has only raced the Tour of Poland in which he was once again the strongest climber. The long, final time trial was costly and so he only finished 5th but he showed that he is ready to lead the British super team in their final grand tour of the season.

The mountainous route suits him down to the ground. He's an explosive climber who can handle both long, gradual ascents and short, steep ramps and the 11 uphill finishes should provide him with plenty of terrain to shine. He thrives on the steepest slopes and has made excessively steep ramps his specialty. It is no wonder that he finished 2nd on the Mur de Huy earlier this year and won that difficult stage of the Vuelta al Pais Vasco. The course offers plenty of very steep finishing limbs - Valdepenas de Jaen, Alto de Hazallanas, Pena Cabarga and Angliru - and so he could not have designed a more favourable course. With bonus seconds on offer, he has a big chance to gain plenty of time along the way and will maybe even challenge Joaquim Rodriguez in his trademark finishes in Valdepenas de Jaen and on Pena Cabarga.

His main weakness is of course the time trial but he has a reason to stay optimistic in that regard. Not only is the number of kilometres against the clock very limited, the course is also very hilly. Furthermore, he is much stronger in the discipline than most would suggest. He finished an incredible 9th in the long Giro time trial which had a climb in the end and a technical beginning but also a long flat stretch at the midpoint. He had a fine ride in Poland where he finished 17th on a course that didn't do him many favours and he defended himself well on the hilly course in the Vuelta al Pais Vasco by finishing 7th. At the same time, he backed by an incredibly strong Sky team which will be one of the favourites for the team time trial, thus allowing him to take back some of the time he may lose in the time trial.

He will line up alongside close friend Rigoberto Uran who finished 2nd in the Giro but the team has made it clear that it will be all for Henao during those three weeks in Spain. Uran's decision to leave the team may have played a role in reaching that decision but the team has every reason to believe more in Henao than in the Giro runner-up. Uran has never been able to match the best climbers in the world and he was certainly not the second best climber in the Giro. On the contrary, Henao dropped the best riders in the Basque Country earlier this year and appears to have progressed since. The 2013 Tour de France put Nairo Quintana in the spotlight for a broader cycling audience. The 2013 Vuelta a Espana is likely to be the race that reveals the talents of another Colombian climber.

Joaquim Rodriguez (****)

During the early part of his career, it was not at all obvious that Joaquim Rodriguez would develop into one of the best grand tour riders in the world. Being a formidable classics rider and stage hunter in the biggest races, he was hugely inconsistent during the three-week events and was mostly unable to handle long, gradual climbs as opposed to the short, steep ramps on which he thrived.

A dedicated effort to develop into a rider also for the high mountains, improve his poor time trialling ability immensely and get rid of his numerous bad days has seen him step onto the  podium in his three most recent grand tours - always on the lowest step - and so it is completely justified that he enters this year's Vuelta a Espana as one of the obvious race favourites.

He had come close on a number of occasions but last year he finally stepped into the world elite of grand tour riders. He had no bad day at neither the Giro nor the Vuelta and he even finished 7th in the long time trial at the Vuelta - a performance that was not even comparable to the one that had seen him lose more than 6 minutes 2 years earlier. While his climbing was not outstanding at the Giro, he was doubtlessly the best rider in the Vuelta mountains and only a bold move by Contador on an intermediate stage that was completely unsuited to Rodriguez' characteristics, saw the Katusha rider miss out on the win.

This year's mountainous Tour route has seen him skip his usual Giro-Vuelta double and he made his only second appearance at the world's biggest bike race this summer. Having always timed his condition to perfection, it was a surprise to see him struggle through the Pyrenees and when he also lost plenty of time in the flat time trial, he had almost completely fallen out of podium contention. When his legs finally came around for the very difficult final week, he confirmed that he has developed into one of the very best climbers in the world - also on longer climbs which had previously been his weakness - and he even managed to drop Chris Froome on the Annecy-Semnoz climb despite doing all the work in the front trio.

Earlier in his career, he always struggled on longer, less steep climbs and always had at least one bad day. Three times in a row he has proved to have overcome those difficulties and as he has also increased his climbing level a further notch, it now seems unlikely that the Spaniard will not win a grand tour at some point in his career.

Based on his performances in the Tour de France and the nature of this year's Vuelta course, he would probably have been the favourite to win the race, had all riders been on equal terms. With 11 uphill finishes, he has plenty of terrain to shine and Valdepenas de Jaen, Alto de Hazallanas, Pena Cabarga and Angliru all offer him those extremely steep finishing climbs on which he thrives. With bonus seconds on offer and a strong Katusha team to support him, all would be set for a completely dominant show in the mountains.

At the same time, the hilly time trial suits him well. Famously known for his disastrous time trials, the Spaniard has done a huge work to improve his weakness and the results prove that his efforts haven't been in vain. On hilly courses, he is actually now a rather strong time triallist as was proved by his 3rd place in the final Tour time trial, 7th place in last year's Vuelta time trial and 6th place in last year's Vuelta al Pais Vasco time trial. The climb on this year's course doesn't suit him well but it should allow him to limit his losses. At the same time, none of the GC contenders are outstanding time triallists. On paper, this year's race offers him the best ever chance to win the race.

When he isn't the favourite to win, it is due to his racing schedule. Rodriguez knows that the Tour-Vuelta double is a difficult combination and so he has tried to limit his racing all season. He raced less during the spring season than he would have preferred and he hasn't raced at all since he rolled onto the Champs-Elysees one month ago. However, no rider has won the Vuelta on the back of a top performance in the Tour during the last decade. Chris Froome tried to do it last year but faded dramatically during the third week of the Vuelta, ultimately finishing 4th. The Brit had to deal with the Olympics in between his grand tours and that should allow Rodriguez to be a little more fresh than Froome was one year ago. On the other hand, Rodriguez has also targeted the spring classics and so has had more racing during the early season than Froome had last year.

However, Rodriguez may be the man to buck the trend. When he last raced the Tour in 2010, he went on from his 7th place finish to take 4th at the Vuelta. This suggests that he may accomplish the feat but he will have to do what no one has managed in the early part of this millennium. The likely outcome is that he will pay the price and get back to his habit of having a bad day during the important third week of the race and so he may throw away what could have been his best ever chance of winning a grand tour.