It's not, of course.
Pulled muscle. Not surprising that a 35 year old can get injured.
I agree with Snowwy on this one. Why not try to win the match despite the injury? It's not like he has much of a career to jeopardize in front of him...he's 35.
By retiring at this stage it just shows that he doesn't care about the results anymore. In my opinion, he can now be a club player, instead of a professional. The way the draws fall and the way the matches transpire matters to a lot of people (not just gamblers) and retiring at this stage of the match sends a strange message to fans, tournament organizers and other players. Plus he retired at this challenger last year, while up in the first set. Barring a serious injury where Suzuki actually couldn't play (which is very possible, and maybe someone that watched the match can fill us in ), I find this to be stupid behavior. Just try to beat the guy if he did not actually earn a position in the next round.