As you probably know, the Blue Jays recently acquired David Price. He is what sportswriters call a “rental”: his contract expires at the end of the season, and he will become a free agent. It will likely cost some team a lot of money to get his signature on a contract – Jon Lester, who is about as good as Price, is guaranteed $145 million to pitch for the Chicago Cubs for the next six years.
Since there’s a real possibility that the Jays won’t want to sign Price, they have no real incentive to not wear him out, other than that overworking him might mean that other star pitchers will ask for no-trade clauses to Toronto in their contracts. It’s in their best interest to pitch him as much as possible, and it’s in his best interest (from a strictly monetary point of view) to work as little as he can.
Of course, he might be willing to push himself – elite major league ballplayers are competitors, and flags fly forever. But $145 million is a lot of money.