I´ve never had the impression that he was overweight or even out of shape or slow.
Of course, he was injured for a long time and is now back since a few weeks and tries to get back into the rhythm, but as Dortmund doesn´t play twice per week, this drum beats a different beat, for now.
He is experienced even at his young age (24). He came to Dortmund four years ago, won the league championship, DFB cup, sadly missed the WC last year due to injury (he would have been there for sure) and played in the CL final.
After being back now from injury, he is back with Jogi´s team Germany again. Problem with him is he is prone to injury, it seems (don´t remember any injury, but there were quite a few - he played in less Bundesliga matches in the last two seasons combined (1+19) than the two years before, although he never played in 30 league matches per season. His best season should have been Dortmunds CL final season, when he also played his most matches, 28 in the Bundesliga and 12 in Uefa CL, which got him the kicker-ranking "world class" ahead of next season.
I think it was more important to get the minutes played in 2015 without getting a new injury.
His best position is of course the defensive midfield, but in earlier seasons, Klopp also played him as a more offensive option behind the strikers (you could say as a playmaker). If you wanna compare him to others at the position, he will probably be one of the most creative players in the position and very dangerous in front of the goal. He is able to play good short passes and also tries the long ball, which is of course a very often used way of attacking in Dortmund. His biggest negative is that he plays a ball-winning position in the defensive midfield, but he isn´t a very physical option like a Sami Khedira or Schweinsteiger (maybe it´s unfair to compare him to those guys, but you have to compare him to the best at doing some things).
http://www.kicker.de/news/fussball/bundesliga/vereine/2014-15/48408/vereinsspieler_ilkay-guendogan.html When i check his tackling stats (see: Zweikampfquote), at each level (DFB Pokal 45%, 1.BL:43%, CL:41%), he is below average and wins less than other midfielders (other than DFB cup, where they also win 45%).
[--> For example, Sebastian Rode, a decent defensive MF from Bayern i checked, wins 57% of tackles in CL, 56% in DFB cup and 57% in Bundesliga.]
He just seems like he has average tackling stats, in every season. I don´t know what to make of this, if this somehow comes from Dortmunds way to play or whatever.
His contract runs until 2016, Dortmund offered him a new one, but he refused to sign it. It is clear that he leaves and Dortmund and him have said the last few days they are moving on. It was said a few weeks ago if he leaves (before it was said that he really leaves...
), that he may leave for about 30mil.€, which i think is very, very high for a guy with only one year remaining on his contract, but other sources said it would be a bargain for teams to get him for that sum.
Someone on a german forum said, he can envision him on Wolfsburg. They don´t have much depth (just Luiz Gustavo as a great player) in defensive midfield, but i don´t know if 1)they spend another 30mil on a single player and 2)Dortmund would sell Gündogan to them or just let him go to another team for 1mil less.
I think he would be better off with Wolfsburg and playing in a league and opponents he knows, instead of going to Spain or England because there is 2mil.€more per season to earn, but sit on the bench at Manchester City, for example.