MINNEAPOLIS — Shoulder rehabilitation progress for Minnesota Twins left-hander Glen Perkins has been frustratingly slow.

The three-time All-Star closer has not pitched in 388 days and counting, carving a large chunk out of the late stage of his career.

“I feel like I’ve plateaued a lot here. I’m tired of being on a plateau,” Perkins said. “I want to improve. I don’t want to be plateaued anymore.”

Perkins was set to confer with team doctors to ensure his recovery program remains on the right track and see if there’s a way to give the rehab a jump start. He has an inability to completely “let it go” when he throws in the bullpen, whether because of inflammation or weakness or something else.

“I can confidently say I’m over 50 percent, and I can confidently say I’m under 100 percent,” Perkins said before Minnesota’s game against Oakland on Wednesday. “There’s a wide range in there. I know that long toss is a lot closer to 100 percent than my bullpens have been. I think that’s encouraging and that’s what I’ve been propping myself up with.”

There’s still a long way to go before the 34-year-old Perkins can get back on the mound in a major league game, though. After appearing in only two games last season, Perkins had several setbacks before settling on surgery to repair a torn labrum by Los Angeles Dodgers team physician Dr. Neal ElAttrache, a shoulder specialist.

Perkins is making $6.5 million this year. The Twins have a $6.5 million option on his contract for 2018, with a $700,000 buyout. Brandon Kintzler has capably filled the ninth-inning role since Perkins was hurt last season, and Twins officials have stressed to Perkins to not put a timetable on his return. That’s a difficult temptation to avoid, of course.

“I’ve put timelines on it because I want to play. It’s been over a year since I’ve played baseball,” said Perkins, a lifelong Minnesotan and former first-round draft pick who has spent his entire career in the Twins organization. “That’s been my motivation, to try and get back and get back as quickly and as safely as I can. It’s frustrating when you don’t reach the goals that you set.”

Perkins converted all 28 save tries before the All-Star break in 2015, posting a 1.21 ERA. Bothered by back and neck trouble down the stretch that season, Perkins was limited to 22 appearances in the second half. He had a 7.32 ERA, blowing three of seven save chances.

“I’ve been banging my head against the wall,” Perkins said. “I’d like to be further along than I am, but that’s just how it goes.”