Well, this isn't something you see every day: a first-place team trading an every-day player in the middle of a hot pennant race ...

But it's not like Johnson has been indispensable this season. After playing brilliantly last season, his first with the Diamondbacks, Johnson has struggled through a perfectly schizophrenic 2011: terrible in April, good in May, terrible in June, good in July, and now worse than terrible in August.

The Blue Jays obviously don't "need" Johnson, as they're basically stuck in fourth place and Johnson's eligible for free agency after this season. It looks like this deal, for the Jays, is purely about collecting a pick in next year's draft if Johnson is offered arbitration and opts instead for free agency. But will the Blue Jays actually risk the possibility that Johnson will accept arbitration, and earn perhaps $8 million next season?

The Diamondbacks are taking a risk here, too. Aaron Hill, an All-Star who hit 36 home runs just two seasons ago, has a .213/.271/.359 batting line since. Meanwhile, McDonald is a 36-year-old utility infielder with a .276 career on-base percentage. While Willie Bloomquist isn't exactly the perfect replacement for injured shortstop Stephen Drew -- out for the season after suffering a gruesome ankle injury -- it's hard to figure what McDonald brings to the table, except perhaps some late-innings defense.

Essentially, the Blue Jays have traded two players they didn't want for a potential draft pick, and the Diamondbacks are just hoping that Aaron Hill somehow remembers how to hit.