Six weeks remain until the July 31 non-waiver trade deadline, which puts several clubs on the clock to decide whether they’ll buy or sell. The parity we’ve seen in Major League Baseball has a long list of teams in contention as we approach the All-Star break, making for a strong seller's market.

Using the average Major League OPS by position*, I’ve identified what holes exist on teams that remain in playoff contention. To cut some of the fat, I'm not going to label a team five games or more out of the Wild Card race as a contender. In the American League that means the Indians, Mariners, White Sox, Red Sox and Athletics won’t be buyers. In the National League that list includes the Padres, Reds, Marlins, Rockies, Brewers and Phillies.

Arizona: Second Base

If the Diamondbacks decide they can make a run for a playoff spot, however unlikely, making a change at second base might be the easiest fix. Chris Owings had absorbed 213 plate appearances at the position and has an ugly slash line of .233/.326/.577. Aaron Hill, Cliff Pennington and the like haven't hit well either.

Atlanta: Left Field

The Braves were supposed to be terrible, but that's been far from the case. They have strong pitching, which makes them dangerous as we get closer and closer to September. The issue has been left field, which has been manned by Jonny Gomes, Kelly Johnson and Todd Cunningham. Johnson (.252/.294/.437) has been the best of the lot and there is still plenty of room for improvement.

Baltimore: Shortstop

J.J. Hardy has been great for the Orioles, but injuries and ineffectiveness have plagued him in 2015. Baltimore has gotten a .565 OPS from the shortstop position, thanks in large part to Hardy (.241/.260/.310) and Everth Cabrera (.208/.250/.229). This is the lightest-hitting positing in baseball, but still a position that the Orioles can improve.

Chicago Cubs: Second Base, Center

Chicago may not have expected to compete for a playoff spot, but they are very much in the thick of the hunt as July approaches. The Cubs have given a majority of their second base at-bats to Addison Russell, who is just 21, but that and center have room for improvement. Theo Epstein can either let Russell mature or acquire help for the stretch run.

Detroit: Third, DH

Brad Ausmus insists that the Tigers are going to stick with Nick Castellanos, but he has been one of the few holes in the lineup. The 23-year-old is hitting .217/.267/.328 in 255 plate appearances. A reliable third baseman could help Detroit leapfrog Minnesota and/or Kansas City in the AL Central.

Houston: Third Base

The Astros lead the AL West and other than upgrading the starting rotation, third base should be Jeff Luhnow's focus. They’ve been relying on Luis Valbuena (.186/.262/.428) too much. Maybe a position shift occurs with Carlos Correa and Jed Lowrie when the latter returns to health, but something must be done.

Kansas City: Second (.553)

Kansas City is more than 10 games over .500, but Omar Infante has been well below average at second. In 228 plate appearances, he’s hitting .230/.237/.311 with just 16 extra base hits. If the Royals want to get back to the World Series an upgrade at second might help.

Los Angeles Angels: Catcher, Short, Left, DH

Mike Trout and Albert Pujols have shouldered the load in L.A., but Jerry Dipoto has several options to bolster his offense. The Angels have gotten a below-average OPS from catcher, shortstop, left field and designated hitter. It’s troubling that DH is on that list, but it’s also one of the easiest positions to improve because there is no defensive specialty. All Dipoto has to do is acquire a hitter of any kind.

Los Angeles Dodgers: Short

Jimmy Rollins could be playing alongside longtime teammates Chase Utley and Ryan Howard losing in Philadelphia, but he hit the jackpot and could log some playoff at-bats in Los Angeles. The problem? The 36-year-old shortstop is hitting .211/.269/.344 in 269 PAs.

Minnesota: Catcher, First, Center, DH

Like the Angels, the Twins are hovering above .500 despite getting below-average production from nearly half of their lineup. Unlike Los Angeles, Minnesota doesn’t have the one-two punch of Trout and Pujols. They might be smart to sell rather than buy, but if they choose to add there are quite a few options.

New York Mets: Catcher, Center

Of all the teams on this list, the Mets may have the most riding on the line as the deadline approaches. They have a potentially dominating starting rotation, which can win you a World Series. Sandy Alderson might sleep better if he can get more production up the middle though.

New York Yankees: Second, Third

Stephen Drew has hit 11 home runs, but has a damaging .190/.258/.389 slash line and Chase Headley has disappointed after re-signing with the Yankees. If only Alex Rodriguez could play some third base.

Pittsburgh: Short, Right

The Pirates may have to settle for a Wild Card berth, but can solidify their playoff position with an upgrade over Jordy Mercer (.555 OPS) in the infield. Gregory Polanco has struggled, but the 23-year-old is part of the future.

San Francisco: Center

Bruce Bochy is getting great production from the infield, but Angel Pagan has hurt them in center (.273/.306/.331).

St. Louis: First

The Cardinals always find a way, but haven’t recovered from Matt Adams’ injury and could use help at first. Mark Reynolds could catch fire, but adding someone else is probably a better option.

Tampa Bay: Catcher, First, Short

The Rays lead the AL East on the strength of their pitching -- they are well over .500 but have just a +16 run differential. Some offensive help could be all they need to grab hold of the division and make a surprise playoff appearance.

Texas: Second

Texas has used Rougned Odor, Hanser Alberto, Adam Rosales and Thomas Field at second in 2015. What's another option, right?

Toronto: Center

The Blue Jays need pitching. They need pitching badly, but replacing Kevin Pillar in center could make the most dangerous lineup in baseball unstoppable. They also need pitching. Pitching.

Washington: First, Left

Washington has enough talent to lead the NL East despite a slow start, but there are places in which they can further fortify. Ryan Zimmerman and Jayson Werth are currently on the DL, but neither was hitting all that well before their respective injuries. Considering a platoon option at the very least would be beneficial as they work their way back in the lineup.

*For reference here is the average OPS in the Major Leagues this season (through June 18) by position: Catcher: .671, First Base: .803, Second Base: .690, Third Base: .749, Shortstop: .668, Left Field: .709, Center Field: .726, Right Field: .763, Designated Hitter: .739.