Who would be a good opponent for Floyd Mayweather's tune-up fight for Manny Pacquiao?

The fighter that Pac just beat to win a version of the welter title, it will show us and Floyd how much he has less, but he`s getting older by the month so a tune up fight might not be a good idea as there is so much time in between fights, he should spar with McGregor in the build up though because he`s a southpaw like Pac and gave Floyd the run around for a few rounds, I feel they should fight an exibition instead.