For me, right now, it's a team mate.
He's a few years younger than me (most are) and he has a killer pop.
If it comes down to a sprint the only way I can beat him is if the sprint starts about 800m out or if there are a ton of attacks in the last 2 or 3 kms.
The only way I can really beat him is to get into a break. This is always my preference anyway. And, if it comes down to the last 5km and we're in the same group, I'm going to lead the guy out because we'll most likely crush anyone else there.
It's a pretty wierd situation to be in.
At the last RR I wanted to do something with about 60km to go but he slipped of the front (marking a guy) and I was forced to block for him because they made it across to the break. The good thing is he won but I ended up getting mangled in the sprint and managed a 5th.
I really wanted that one, too.
I guess it's better to be racing with him than against him...