Who's indispensable for contenders down the stretch?

Nolan Arenado will be crucial to the Rockies' bid to return to the postseason. Jayne Kamin-Oncea/USA Today Sports

Which players in baseball are most important for their teams down the stretch? The answer is trickier than simply picking the league's best players, because as we head toward the final quarter of the season, half the teams are practically -- though not mathematically -- eliminated from playoff consideration. Add in a few more heavy playoff favorites -- J.D. Martinez and Mookie Betts could retire tomorrow to operate a food truck and not prevent Boston from reaching the postseason -- and you're looking only at a subset of great players who actually remain playoff-relevant.

For each team's best players, I ran the difference in postseason probability with and without the player in question, with the replacement player coming from whom the organization has on hand rather than a literal replacement-level player. This consideration is more important than it was a few weeks ago because now there is no price a contender can pay to trade for Manny Machado or Noah Syndergaard or J.T. Realmuto.

10. RHP Zack Greinke, Arizona Diamondbacks
Playoff odds impact: Adds 10.6 percent

With the Rockies showing a pulse in the last month or so and the Dodgers not falling back again despite their usual rash of injuries, Arizona's playoff hopes remain up in the air. The team quietly improved with a few moves at the trade deadline, but it still lacks enough minor league depth to fill in any holes. Losing Greinke would put a big dent in Arizona's chances, but at least the Diamondbacks still would have Patrick Corbin, Zack Godley, Robbie Ray and the shockingly decent Clay Buchholz in their rotation.