Talking to fellow Chelsea fans, and browsing through various blogs, I gather that a majority of Blues fans don't want the Brazilian born Spanish international at the Bridge. The main worry is the fact that he is having a freak season, with no guarantee he will be able to be as prolific going forward. I must say that's a fair question; however I completely disagree with the idea that Costa is having his first breakout season.
Costa is and has been a top quality player for a while, and the world outside la liga is just now taking notice because he has been scoring at an alarming rate this season. In order to prove so, let's take a look at his stats (Courtesy of espnfc.com). During the 2009-10 season in la Liga, the hot-headed Brazilian come Spanish player scored 9 goals in 33 games started for Real Valladoid. The following year, he registered 8 goals in 17 games started for Athletico Madrid. In the 2011-12 season, he had 10 goals and 4 assists in 15 games started on loan for Rayo Vallacano, and only started one game from the bench. From 2009 to 2012, Diego Costa had consistent and decent numbers for a support forward. However, if any season was to be considered his breakout season, it would definitely be his 2012-13 season.
Back at Athletico, the powerful striker scored 20 goals, and had 8 assists in 36 starts for the Madrid club in all competitions. Given the fact that he was playing either as a wide forward or as a support striker to Radamel Falcao, these are outstanding stats. Many in Spain argued that Costa was the team's most influential forward, ahead of Falcao and frankly, having watched them play on many occasions last year, I can understand why. What these outstanding numbers don't capture however, is his work rate and link-up play which allowed the team to get the best out of the fox in the box that is Falcao. When quizzed about him, here is what Osasuna defender Alejandro Arriba had to say: "I think that Diego Costa is now even more important than Falcao, for he is in great form [...] I know him from last season, when we were at Rayo, and I think that he is a key player for any team. He is now at the highest level and is key to Atletico Madrid" (courtesy of Football Espana).
This Season, Costa has been asked to fill the void left by Falcao. He is now playing as the club's main man within a stoke duo, and therefore has been tasked with greater goal-scoring responsibilities than in previous years. He has stepped up to the plate and contributed 25 goals and 4 assists in 32 starts thus far. Not too shabby.
I can't say that I've followed Costa from the beginning of his career, but I've certainly watched him throughout all of last season, and having done a little research on him, I can say with confidence that he is not having his one and only season at a top performing level; he has already proved that he is no one season wonder. The stats are there to back his consistent improvement, and let's remember that he is only 25 years old, with still much room for further amelioration.