BRADENTON, Fla. -- Jeff Locke felt it lifting weights last July. Coming up from a squat, he never made it to the top.

No noise, no pop, but he instantly felt a sharp pain.

"I couldn't really walk for a few days," Locke said.

The back injury forced Locke to miss his final start before the All-Star break and kept him from participating in his first All-Star game. He was able to pitch in the second half of 2013, but the back injury, he said, limited his preparation between starts.

Locke refuses to make excuses, but his performance dropped sharply in the second half. Entering spring training, Locke plans to gain strength and avoid the cocktail of circumstances that plagued him after midseason.

"Maybe because last year in the second half, we slowed it down so much, I felt like maybe this offseason I had to push a little bit more," Locke said. "It's tough in November and December to be in the weight room and be like, 'I got to push it for August!' But if I didn't go through what I went through, I probably wouldn't have [pushed harder.]."

The 26-year-old Locke, a slender lefty, earned the final spot in the rotation out of spring training last season. He hit his stride in his fourth start of the season, when he allowed two hits in six scoreless innings against the Philadelphia Phillies in Citizens Bank Park, and never looked back. Eleven of his 18 first-half starts lasted at least six innings and four of his final five starts went for seven innings or more. He arrived at the break with a 2.15 ERA in 109 innings.

Then came the back injury, which forced Locke to miss his final start of the first half.

"That was the only thing that really upset me," Locke said. "I've never missed a start in my life. That was the first one. Every time they've said, 'Hey, you're taking the ball,' I've taken it. That's something I've always prided myself on."

During the second half, Locke said, he remained able to pitch but had to reduce his workouts during the four days between starts. The limited work meant Locke became fatigued as the season wore on. His ERA in the second half jumped to 6.12.

"To be honest with you, the first half and the second half, I don't think they were that much different in the ways I pitched," he said. "Now, the results were way different, but every stat rat in the world anyway was just waiting for it to happen."

To prevent future back issues, Locke spoke to players who had overcome back problems to discover how they maintained themselves. He learned more about his body's kinetic chain and how tightness in other muscle groups, such as his hamstrings, can affect his back. He added some weight.

"I think every time I think about last season, the only thing I wonder, really, is how much different it could have been if I was still pitching the same way at the end," Locke said. "You put a lot of pressure on yourself to come back this year and say, 'I'm not going to let the guys down again like last year.' I let myself down."

Locke began throwing off a mound a few weeks before spring training began. He throws at moderate intensity and limits himself to four-seam fastballs and changeups.

"That's something that A.J. [Burnett] always told us," Locke said. "'That guy's coming in right out of the gate throwing hammers. Where's that going to be in September, or August?'"

The final two spots in the Pirates' rotation, after Francisco Liriano, Gerrit Cole and Charlie Morton, appear somewhat fluid. Wandy Rodriguez will return to the unit if he feels no ill effects from the injury to the flexor tendon in his left forearm that kept him out for the final four months of 2013. The Pirates spent $5 million on Edinson Volquez, who allowed more earned runs last season than anyone in the National League and hasn't had an ERA of less than 4.00 since 2008.

Locke will compete for one of the final two spots. Even if the back injury reduced his workload between starts and affected his performance, he still has other issues to address. After walking 47 batters in 109 first-half innings, Locke walked 37 in 571/3 innings in the second half. Opposing batters hit .308 against him, up from .202 before the All-Star break.

"I just wanted to gain strength so that down the stretch next year, this coming season, if fatigue played a part last year or if it was just my back, I wanted it to not be because of the fatigue," Locke said.

The intent, at least, is to make it back to the top.

First Published: February 16, 2014, 2:50 a.m.