By Cliff Corcoran

June is upon us, and in the next month and a half, every team in baseball is going to have to decide whether or not it will be looking to buy or sell talent prior to the non-waiver trading deadline on July 31. That decision will be particularly difficult for some of the teams that have exceeded expectations early this season. Buying into their success would increase their chances of sustaining it, but a misjudgment could prove disastrous, costing those teams both a chance to cash in on valuable veterans who could leave as free agents in the fall as well as potentially useful prospects, hurting their longer-term rebuilding strategy.

With that in mind, here's a quick look at the scenario being confronted by this season's six most surprising teams, listed here in order of their winning percentage entering Thursday's action.

New York Yankees

Record: 30-20 (.600), 1st place AL East, 2 games up
Playoff odds: 67.6%
Walk-year veterans: OF/1B Matt Holliday, SP Michael Pineda, RP Tyler Clippard
Biggest need: Starting pitching

New York's offense seems likely to cool off as the season progresses, powered as it has been by outsized performances from rookie Aaron Judge, the formerly slap-hitting Brett Gardner, 37-year-old Holliday, and an erratic Starlin Castro. Still, only the Nationals and Astros have scored more runs per game this season than the Yankees (Houston via a 17-run outburst Tuesday night), and the advanced metrics are buying what the Bronx Bombers are selling, with Baseball Prospectus giving New York the best chance of any of the six teams on this list of making the postseason.

Better yet, the Yankees have one of the deepest farm systems in baseball from which to make a deal, and their biggest need is starting pitching, something this season's market has in abundance. Yu Darvish is the sexiest name out there, but lefty Jaime Garcia is pitching well for the Braves, Jason Vargas has had a remarkable comeback season thus far with the Royals, Scott Feldman has been a solid contributor in the Reds' rotation, and Derek Holland is off to a great start with the White Sox. Those are just five quality starters headed for free agency this fall, if some of the other teams on this list fade from contention. The Yankees also have the chips to make a play for a multi-year addition such as Jose Quintana, Justin Verlander or Sonny Gray, none of which would likely cost a huge prospect haul. The Yanks will be active at the Trade Deadline.

Arizona Diamondbacks

Record: 33-22 (.600), tied, 2nd place NL West, 1/2 game back
Playoff odds: 73.3%
Walk-year veterans: C Chris Iannetta, RPs Fernando Rodney, Jorge De La Rosa, Tom Wilhelmsen
Biggest need: high-end relievers

First of all, none of those walk-year veterans have any significant trade value, so the D-backs can safely go all-in at the Deadline. That's a decision they would likely have made either way, as rookie manager Torey Lovullo has them running like a finely-tuned machine. Arizona's hardest decision will be figuring out what exactly it is they need. Assuming A.J. Pollock and Taijuan Walker make prompt returns from minor injuries (a groin strain and a blister, respectively), the team's biggest need right now would appear to be in the bullpen, which lacks an elite reliever. Potential walk-year targets there include veteran sidearmers Pat Neshek and Joe Smith, Pittsburgh's Juan Nicasio (who has yet to allow a home run in 23 2/3 innings this season), and righty Anthony Swarzak, who is having a career year with the White Sox. Even more compelling are closers Kelvin Herrera, David Robertson, and Jim Johnson and A's set-up man Ryan Madson, all of whom would remain under team control in 2018. Of course, those four would be correspondingly more expensive.

Colorado Rockies

Record: 33-22 (.600), tied, 2nd place NL West, 1/2 game back
Playoff odds: 65.7%
Walk-year veterans: OF Carlos Gonzalez, 1B Mark Reynolds, RP Jake McGee, SP Tyler Chatwood
Biggest need: More production from outfield corners

The Rockies have scored more than five runs per game thus far this season, but they can thank their home ballpark for much of that. Their park-adjusted team OPS+ of 89 is fifth-worst in the Majors. The trick is that their weakest offensive positions thus far have been the corner-outfield spots manned by Carlos Gonzalez and Ian Desmond, two players unlikely to be replaced by Deadline additions, and they could get sophomore outfielder David Dahl back from the disabled list sometime in June. The flip side is that with Gonzalez scuffling, he's unlikely to draw much interest as a two-month rental for another contender. The Rockies have some talent on the farm that could be dealt, but they're probably better off going small here. A deal for a multi-position or part-time bat such as Howie Kendrick would likely be the best fit. That said, don't rule out a bigger splash for an upgrade to the starting rotation should they be in as strong a position in mid-July as they are now.

Milwaukee Brewers

Record: 28-25 (.528), 1st place NL Central, 1.5 games up
Playoff odds: 31.1%
Walk-year veterans: UT Eric Sogard, RP Neftali Feliz
Biggest need: left-handed relief pitching

Having already sold off all of their best trade chips, the Brewers have no opportunity cost should they decide not to sell yet again (no, Ryan Braun, who is still owed $57 million beyond this season and has hit the DL twice this month with a calf strain, isn't getting traded this year, either). The big question is if they should buy or stand pat and continue to let their farm develop. Certainly, it would be foolish to trade one of their better prospects for the short-term relief help that could keep them in the NL Wild Card hunt. Yet, if they can get someone like the Padres' Brad Hand (an increasingly dominant lefty with two more team controlled years beyond this one), the Mets' Jerry Blevins (who has a $7 million club option for 2018), or the Mariners' Marc Rzepczynski (who is under contract for $5.5 million in 2018), for a package of second-tier prospects, that might be a worthwhile investment.

Minnesota Twins

Record: 26-23 (.531), tied for 1st place in AL Central
Playoff odds: 25.6%
Walk-year veterans: SP Hector Santiago, RPs Brandon Kintzler and Craig Breslow
Biggest need: pitchers, specifically at least one starter and one right-handed reliever

The Twins have two huge trade chips not listed above who won't be free agents until after next season. Those are default ace Ervin Santana, who is currently leading the majors in ERA (1.75) and WHIP (0.84) and will never be more valuable on the market than he is right now, and second baseman Brian Dozier. Kintzler and Breslow are also having nice seasons, the former as the closer for a first-place team. So, in contrast to the D-backs, there is some opportunity cost to being a buyer here. Making that decision even more difficult is the general pessimism about the Twins' ability to sustain their May surge. The Twins went 17-8 from April 24 to May 24, but are 9-15 on the rest of the season, including an active four-game losing streak. For all of the narratives about how they are winning with great defense, they have allowed 5.08 runs per game on the season, dead last in the American League. It's obvious that they need pitching to back up Santana and rookie Jose Berrios (both of whom have indeed benefitted greatly from the performance of their fielders) in the rotation as well as in the bullpen to accompany Kintzler and lefties Breslow and Taylor Rogers. However, it's not clear yet that the investment to get those pieces is warranted, as the Twins would need to make multiple additions to their pitching staff to resemble a serious contender. They might be better off standing pat and targeting those pitching needs in the offseason, when the players they acquire will be more than short-term rentals.

Baltimore Orioles

Record: 27-24 (.529), 3rd place AL East, 3.5 games back
Playoff odds: 11.7%
Walk-year veterans: OFs Seth Smith and Hyun-soo Kim, SP Chris Tillman, RHP Ubaldo Jimenez
Biggest need: starting pitching

The Orioles have been in free-fall, going 5-14 since May 10. However, they just took two of three from the first-place Yankees to keep ahead of the climbing Rays in the AL East, and their pending free agents above are all having seasons that fall somewhere between disappointing and lousy, undermining their market value. With Manny Machado under team control for just one more year after this one, it wouldn't be shocking to see Baltimore go for it despite their poor overall prognosis. If they do, their best strategy would be to upgrade their starting rotation and hope the veterans in their lineup, Machado included, can return to form at the plate. Next year, however, a poor first half could lead to the dissolution of the team, with Machado, Adam Jones and Zach Britton all in their walk years.

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Cliff Corcoran is a Sports on Earth contributor and a regular guest analyst on the MLB Network. An editor or contributor to 13 books about baseball, including seven Baseball Prospectus annuals, he spent the last 10 seasons covering baseball for SI.com and has also written for USA Today and SB Nation, among others.