The first day's Davis Cup action this weekend could see history in the making, when Federer takes on Mackin. I cannot find any bookies offering odds on Federer - although British betting exchange Betfair has listed the match for trading.
51,805 pounds has been matched at 1.01, but since that has dried up, the only way to bet on Federer is to lay Mackin at 200 - which is the equivalent of backing Federer @ 1.005
If you think Federer will win without dropping a set, then you may think that the 1.02 on offer about him is value.
Keep in mind, that if Roger hurts himself and is forced to retire, the 1 set complete rule comes into play...