3 Cubs who contributed to the team's September collapse

2. Mark Leiter Jr.

Mark Leiter Jr. has been a solid relief arm all year for the Cubs and he emerged out of nowhere to help solidify the Cubs' bullpen. But he hasn't been sharp recently and he appears to be running out of gas in his first full year in the majors.

In the month of September, Leiter owns a 9.45 ERA and his strikeout rate has plummeted to just 8.8 percent. In fact, in his nine appearances this month Leiter has had just one clean outing against the Arizona Diamondbacks on Sept. 16.

With Alzolay's injury earlier this month, the team needed Leiter to step into a bigger role and he has instead faltered at every turn. The bullpen has been a massive part of the team's collapse in September and Leiter is a main culprit.