Remember that Michael Ballack testimonial match? Andre Schürrle played in it; Jose Mourinho was there, and many assumed that something would be worked out between Bayer Leverkusen and Chelsea regarding the former's transfer immediately after the game, mostly because they don't really understand the who 'director of football' thing. But although said match didn't have much impact in the Blues' negotiations with Schürrle's soon-to-be-former team, it wasn't entirely irrelevant:
Mourinho has a great personality and is just a cool guy.
He gave me a handshake when we were at Michael Ballack’s testimonial game, and said “it’s OK, soon you’ll be with me”. It gave me a lot of pride and was a great feeling.
-Schürrle. Source: Bild (paywall) via Metro.
(sorry about the Metro link, but they had quotes so...)
Given the prolonged wrangling over Chelsea's attempted Schürrle purchase -- these rumours have been going for more than a year now -- I don't think the manager could have played this one any better. Schürrle must have been stressed and concerned under his future; Mourinho reassured him that both he and the club valued him highly. For a player who'll almost certainly end up rotated for most of his Chelsea tenure, getting him feeling good early on is a must. Mou did just that here.
I don't think that Mourinho himself had much to do with the transfer, but he'll certainly play a major role in Schürrle's success (or lack thereof) at Chelsea. Motivation will help, and the Special One is a master.