There are currently more than a dozen teams in MLB who are in contention for the division lead or postseason berth. On each of those teams, there is a player who could be considered a potential X-factor in deciding his team's postseason fate.
Here are several players who could play key roles as the season advances toward postseason play.
One of the key contributors to the Red Sox's early success has been Clay Buchholz. The 28-year-old right-hander has been nearly flawless this season, posting a 9-0 record with a 1.71 ERA. Health concerns surround Buchholz, however, as he cut short a bullpen session on Wednesday due to discomfort in his neck.
Buchholz told ESPN that he is still working through discomfort.
"I felt better this time; it's just still there,” Buchholz told ESPN. “We'll see what the staff wants me to do, if there's any way to treat it differently."
A healthy Buchholz could be a deciding X-factor in what is shaping up to be an ultra-competitive AL East. All five teams are within striking distance and are capable of winning the division.
With that in mind, the Red Sox need a healthy Buchholz to contribute.
Ivan Nova could wind up becoming a significant X-factor for the Yankees if their starting rotation encounters any difficulties.
According to Andy McCullough at The Star-Ledger, there is a good chance Yankees manager Joe Girardi could plug Nova in for a spot start sometime in the not-so-distant future.
“We’re just going to go day by day, to see,” Girardi said. “It’s possible he could get another start here. I’m not taking anyone out of the rotation.”
As of this moment, the Yankees have a healthy starting five and Nova is on the outside looking in at the starting rotation. However, with the recent injury history of 41-year-old Andy Pettitte and the weekly ineffectiveness of Phil Hughes, there is a chance Nova could get the call sooner rather than later.
The Rays have an X-factor in waiting in 2012 AL Cy Young Award winner David Price. The 27-year-old southpaw has been on the shelf since May 15 with a left triceps strain.
Price pitched in his second rehab start on Wednesday night and threw 72 pitches over five innings of scoreless ball.
The addition of Price into what amounts to be a strong rotation would be a definite X-factor for the Rays as they enter the second half of the season. The need for him is even greater now that Alex Cobb is expected to miss some time due to a head injury suffered from being hit by a line drive on June 15.
Marc Topkin of the Tampa Bay Times reported that Price will be re-evaluated on Thursday and could join the team next week in Houston.
The Baltimore Orioles have benefited greatly from the offensive output of Chris Davis. He could be a deciding X-factor for the Orioles as they vie for their second consecutive postseason berth.
Davis leads the Orioles in virtually every statistical offensive category (.333 BA, 28 HR, 74 RBI, 1.120 OPS) and is on pace to eclipse Brady Anderson's team record of 50 home runs in a single season. He will need to continue his strong production into the second half if the Orioles have any chance of returning to the postseason.
Jose Reyes' return to the Jays lineup after a two-and-a-half month absence could prove to be a significant X-factor in determining the team's playoff fate in 2013.
Reyes went down with a severe ankle sprain on April 12 in Kansas City. His presence at the top of the lineup as well as his defense were sorely missed. He came back this week, going hitless in four at-bats in his first game against Tampa Bay.
If the Blue Jays are going to return to the playoffs for the first time since 1993, they will need Reyes to come close to his .292 career batting average.
Detroit Tigers catcher Alex Avila has not had a great season to this point. However, he has the potential to be an X-factor for the Tigers in the second half of the season if he can put the poor first half full of injury and missed expectations behind him.
Avila is currently on the 15-day disabled list after being hit on his left forearm on June 17. He currently is on a rehab assignment with the Tigers' Triple-A Toledo affiliate. He has struggled in two rehab games, going 0-for-8 with two strikeouts.
Tigers manager Jim Leyland told Mlive.com that Avila will have to “get his swing going” before he returns to the majors.
A healthy and productive Avila will be key for the Tigers if they expect to put together another successful postseason run. He will need to improve on his poor .172 batting average.
The health and production of Asdrubal Cabrera could ultimately be a key X-factor for the Cleveland Indians as they look to contend for a postseason berth. Cabrera was activated from the disabled list on Wednesday and went 1-for-3 against the Baltimore Orioles.
Terry Francona told the AP that he came back a lot quicker than anticipated. “He's running better now than he was the beginning of the year,” he said.
Cabrera had been on the 15-day DL since June 3 with a strained right quad. His health will be a key for the Indians, as he represents an important part of the lineup. In 53 games prior to injury, Cabrera was batting .254 with five home runs and 25 RBI.
A key X-factor for the Rangers this season will be whether Nelson Cruz misses any time due to his alleged connection with the Miami Biogenesis clinic.
Mac Engel of the Dallas Star-Telegram doesn't think Cruz will miss any time this season. Major League Baseball will take time investigating the allegations before they make any definitive judgments on punishment.
In 76 games, Cruz is batting .268 with 20 home runs and 57 RBI. A loss of Cruz for any significant amount of time could hamper the Rangers' hopes of winning the division and securing a postseason berth.
If the Oakland A’s are going to continue to contend for a postseason berth, they will need offensive production from players like Brandon Moss.
The 29-year-old slugger could emerge as one of the X-factors in a potential Oakland postseason run. Moss belted 21 home runs for the A’s last season and is already on pace to eclipse that mark, with 14 home runs through 73 games.
One of the big storylines from the 2012-13 offseason was the Braves' acquisition of Justin Upton. He opened the first month of the season on a tear, hitting .298 with 12 home runs and 19 RBI. He has, however, cooled off considerably since and has been mired in what has been a two-month slump.
From May 1 to June 25, Upton is batting .209 with three home runs and 15 RBI. He has also struck out 54 times in 205 plate appearances during that span. He will need to become more selective at the plate if he is going to start producing on a consistent basis again.
The Braves have been buoyed by strong starting pitching so far this season, but that doesn’t mean they won’t need more offensive production soon. A real X-factor for Atlanta will be whether Upton can regain his early form and contribute to a Braves stretch run.
One player who needs to remain productive and healthy for the Nationals is second-year star Bryce Harper. He has been missing from the Nats lineup since late May due to bursitis.
Harper is batting .287 with 12 home runs and 23 RBI in 44 games this season. The real X-factor in the NL East race could be whether Harper can stay healthy and add the needed octane to the team's offense.
The St. Louis Cardinals find themselves on top of the NL Central due largely to the strong pitching of Lance Lynn. The 26-year-old right-hander has posted a stellar 10-2 record so far this season and has emerged as one of the best pitchers in the National League.
The real X-factor here is whether Lynn can carry over his dominance into the second half of the season. History seems to suggest that he can, as he compiled an 18-7 record for the Cards in 2012.
It’s easy to draw correlations between the Pittsburgh Pirates and their closer, Jason Grilli. Both are experiencing new-found success after years of endless frustration. The question is, can Grilli and the Pirates maintain their first half momentum into the dog days of summer?
Grilli has been lights out for the Bucs, as he has posted a 0-1 record, 1.82 ERA with 26 saves in 37 appearances. The real X-factor here is whether he can continue this success. If he is able to do so, the Pirates may be able to punch their first postseason dance ticket in two decades.
Aroldis Chapman will prove to be a real X-factor if the Reds continue to contend for the NL Central crown. The 25-year-old closer has pitched well in 2013, posting a 3-3 record with a 2.73 ERA with 19 saves in 36 games.
The Reds will need Chapman to continue to dominate at the back end of the bullpen as they battle the Pirates and Cardinals for the division lead.
It has not been a smooth ride for substitute Diamondbacks closer Heath Bell. Filling in for J.J. Putz as he recovers from a strained elbow, Bell has not been overly impressive. He has a 2-1 record, 4.85 ERA and 14 saves.
Bell can be a real X-factor for the Diamondbacks if Putz is unable to retain his role at the back end of the bullpen. Regardless of whether he finishes out games, Bell will need to raise his game if the Diamondbacks have any chance at securing a postseason spot.
Michael Cuddyer is in unfamiliar territory with the Rockies. He entered play on Thursday with a 23-game hitting streak and the third-best average in the National League at .344.
The real X-factor for Cuddyer and the Rockies will be whether this career .275 hitter can keep this momentum going. The Rockies will need him to contribute if they have any chance of securing a postseason berth.