Should I start Lester Today? Here's the whole situation....

[jway123]

Here's the situation. I'm in a 5x5 head to head league. Today is the last day of the week. The current matchup is as follows for pitching:

Wins - Each have 3
Saves - I'm up 6-0
K's - I'm down 37-31
ERA - I'm leading 3.21 - 4.12
WHIP - I'm leading 1.20 - 1.45

My opponent doesn't have any starters going today. He has 3 relievers, I have 4, all closers. Lester is pitching in Toronto, who has a good offense especially at home. Normally always start my starters, but afraid he could potentially balloon my era and whip today, not sure if i should risk for potential wins and k's victory. Let me know your thoughts.