Jim Riggleman was just on "The Sports Fix" on ESPN Radio 980 with Kevin Sheehan and Thom Loverro, and he confirmed to them that Stephen Strasburg will start every five days, not every five games. This is a slight distinction that will slightly alter the games in which Strasburg is projected to start. 

Via Mark Zuckerman:

Riggleman confirms to Loverro/Sheehan on ESPN 980 that Strasburg will pitch every 5 days til the All-Star break, not every 5 games...

...which means he'll start Sunday in CLE, then Fri 6/18 vs CHW and Wed 6/23 vs KC.