After his next start expect him to be around -14.

During the game he will look like a 30 thus can face 30 batters. Assuming you go 6 innings with 4 batters per inning, his 10 will be at -14 after the game, thus he will need 7 games before starting the next time. If you went all 30 batters, you would be at -20, or need 9 games rest.

The rest cycle is fine for relievers to start. Combine with their limited innings and you need 3 reliever/starters to equal one regular starter.