Reputations can be made -- and unmade -- over these next six weeks. Madison Bumgarner was at his dominating best -- 8-3, 2.29 ERA in 13 starts -- at the end of 2014 as the Giants captured the National League’s second Wild Card berth, and then a World Series title, making them the only team to win the World Series as a Wild Card team since the addition of the Wild Card Game in 2012.

Christian Yelich batted .396 as the Brewers won 23 of 30 to win the NL Central last season. In September 1967, Carl Yastrzemski hit .417 for “The Impossible Dream” Red Sox, who won the AL pennant. For that generation of baseball fans, his stretch of pressure-packed baseball defined a great player being at his best when the stakes could hardly have been higher.

Who is going to be this season’s Bumgarner, Yelich or Yastrzemski? Rather, who must be Bumgarner, Yelich or Yastrzemski to give his team a chance to get to the postseason?

Let’s check out 15 players who may just decide postseason berths:

1) Max Scherzer, RHP, Nationals

If Mad Max is at his best, the Nationals may not just simply make the postseason -- they could be the most serious threat to the Dodgers' quest for a third straight National League pennant.

2) Craig Kimbrel, RHP, Cubs

One of the best closers of all-time may be the difference between the Cubs missing the playoffs and winning the World Series. With him at his best, the Cubs are formidable. Can he still be that guy?

3) Paul Goldschmidt, 1B, Cardinals

Goldschmidt was acquired last offseason for finishes like this one when the Cardinals are hoping to emerge from an insane scramble in which eight teams appear to be fighting for three playoff spots.

4) Brandon Lowe, 2B, Rays

Lowe was the AL Rookie of the Year frontrunner before suffering a bruised right leg in early July. He could return as early as this weekend and could give the Rays offense a needed spark.

5) Lorenzo Cain, CF, Brewers

Cain has played through an assortment of injuries despite spending zero time on the injured list. Manager Craig Counsell has been concerned enough to force him to take three days off that could result in a fast finish.

6) Jose Berrios, RHP, Twins

Berrios has struggled in two of three starts this month, including Saturday, when he could not finish five innings despite being staked to an 8-2 lead against the Rangers in the second inning.

7) Mark Melancon, RHP, Braves

Melancon is three-for-three since becoming Atlanta’s closer, and with the Braves playing the Mets, Nationals and Phillies 20 more times, his ability to hold leads could be huge for the NL postseason picture.

8) Josh Hader, LHP, Brewers

All closers go through tough times. What has made Hader unique is that he’s either missing bats or giving up homers, with no middle ground. Now he’s struggling in a big way, and the Brewers' season may depend on his getting back on track.

9) Tyler Glasnow, RHP, Rays

Glasnow seems confident of a September return from a forearm injury that sidelined him in early May. Until he was injured, he was the American League’s best pitcher (1.86 ERA in eight starts).

10) Edwin Diaz, Mets, RHP

Closer? Setup? Mop-up? Manager Mickey Callaway is attempting to figure out what to do with the guy who was baseball’s best closer last season for the Mariners. He has put together three straight scoreless appearances, and that’s a start for what the Mets need down the stretch.

11) Bryce Harper, RF, Phillies

So much has gone wrong that we’re just going to simplify it: Great players sometimes have the power to almost will their teams to another level. If Harper is able to do it this time, his first year in Philly will be a smashing success.

12) Jose Ramirez, 3B, Indians

The Indians took off right around the time Ramirez snapped out of a two-month slump. This is not a coincidence. When he’s hot, the Indians might be just about unbeatable.

13) Khris Davis, DH, A’s

He has homered once in the last 43 games after hitting 16 in the first 60. The A’s have enough pitching to make the playoffs, and if Davis can get going, they’re capable of beating anyone.

14) Luis Castillo, RHP, Reds

He had a 2.29 ERA before the All-Star break, 5.14 since. Every start is critical as the Reds attempt to stay in the race. Regardless, Cincinnati has 17 games left against the Cardinals, Phillies, Mets and Brewers, so he has a chance to be a difference maker no matter what.

15) Robbie Ray, LHP, D-backs

The D-backs would like to put the proper finishing touch on a season in which they’ve been one of MLB’s most pleasant surprises. To do that, they need Ray back from the injured list by the end of the month, and pitching like the ace he can be.