Fixing a hole: Solving MLB's biggest roster problems

Who should trade for Manny Machado to shore up the left side of their infield? Patrick Semansky/AP Photo

With a quarter of the major league season complete, teams are beginning to separate themselves as contenders and noncontenders, if they had not already committed to rebuilding, or "tanking," in the offseason.

Let's examine the 10 greatest needs among the clubs with 20 percent or greater odds of making the playoffs entering Sunday, according to FanGraphs.

1. The Colorado Rockies (29.4 percent playoff odds) need corner help. According to Baseball Reference-version WAR, the Rockies rank 25th in WAR produced by right fielders (minus-0.3), 28th in left-field WAR (minus-0.4) and last at first base (minus-1.2). This is not a small-sample issue. These are positions that were in need and remain in need.

The Rockies got a weighted runs created (wRC+) mark of 79 from their right fielders last season -- 100 wRC+ is league average -- largely due to Carlos Gonzalez's poor season. They nevertheless brought Gonzalez back on a one-year deal, and he is again struggling. The Rockies ranked 29th among first basemen (87 wRC+) last season. The Rockies signed Ian Desmond to play first base last season, and he struggled, producing a 69 wRC+, which means he was 31 percent below league average when adjusting for the ballpark and scoring environment. This season? He has been historically poor, hitting .175/.219/.365 as his zone contact rate has dropped and his ground ball rate has spiked. He has produced 38 wRC+, which is essentially a pitcher's bat playing at a corner position. David Dahl has not been able to take ownership of a position, as his bat has slumped. In left field, Gerardo Parra hasn't hit.

The Rockies were a wild-card team last year and are contending again in the NL West. They knew these were positions of need and did little to address them. The Rockies were projected by FanGraphs to rank 27th in first-base production (1.0 WAR), 28th among right fielders (0.3) and 30th among left fielders (minus-0.4) entering the season. The good news? Those should be among the easiest positions to fill, as corner bats such as Logan Morrison and Yonder Alonso were modestly valued by the industry in free agency. Targeting the corner players of teams already deep in rebuilds, such as Miami first baseman Justin Bour or White Sox corner bat Matt Davidson, could help fill these voids at relatively affordable returns.