(CBS) After struggling in the second half of the 2015 campaign and often getting an early hook from manager Joe Maddon as the Cubs made their playoff push, right-hander Jason Hammel made changes to his offseason workout regiment in an effort to avoid wearing down in the upcoming 2016 season.

He switched trainers. And most notably, the 33-year-old Hammel’s made a point to improve his lower-body strength.

“I really focused on the lower half, because I just assessed the way I pitched last year and over the last few years, why I’ve kind of hit a road block in the second half,” Hammel said on 670 The Score at the Cubs Convention over the weekend. “I made a small adjustment with the mechanics and really focused on the lower half with lifting this year.

“A lot of people think pitchers, and they just think throwing and that’s where all the power comes from. It’s really not. It starts from the ground up. If you have a strong base, the legs will actually do the work and build all the torque and power you need to throw. So if you have weak legs at the end of the year, that’s not good.

“So I changed that around.”

Hammel went 10-7 with a 3.74 ERA and 1.16 WHIP in 2015, but he noticeably dropped off in the second half. He had a 2.86 ERA and .211 opponents’ batting average prior to the All-Star break, then a 5.10 ERA and .285 opponents’ batting average after it.

Maddon pulled Hammel prior to the fifth inning in five second-half starts, and Hammel only managed to go six or more innings in two of his final 14 starts.

On several occasions in the second half of 2015, Hammel expressed his disappointment in not being given the chance to go deeper in games, though he always handled the situation professionally.

“I’m a pro,” Hammel said. “I understand you check your ego at the door. If you don’t have it that night, you don’t have it that night. But sometimes you’re like, ‘Give me that opportunity to grind through this.'”

Though it appeared Maddon lost some trust in Hammel in 2015, Hammel indicated he’s slotted in the back end of the Cubs’ rotation entering 2016, in some fashion behind the top three of Jake Arrieta, Jon Lester and John Lackey.

“I’m fully expecting to be in the rotation,” Hammel said. “They haven’t told me anything different.”

Still, Hammel will have to earn one of the final two rotation spots amid a competition with Kyle Hendricks and Adam Warren.

Listen to Hammel’s full interview on 670 The Score below.