Grimm’s role changes amid struggles as Cubs try to fix leaky pen

MIAMI – Cubs reliever Justin Grimm, manager Joe Maddon’s “middle-inning closer” from last year, has reached the point with his recent struggles that the manager suggested Thursday he’s willing for now to use the right-hander only in non-pressure situations.

“I’ll probably give him a little breathing room right now and just try to get him back at the right time,” Maddon said the day after Grimm turned a 2-0 game into a rout with a poor sixth inning against the Cardinals.

Grimm’s not the only member of the pen to struggle recently. When Pedro Strop gave up two eighth-inning runs to lose Thursday’s game in Miami 4-2, the Cubs’ bullpen ERA for the last eight games rose to 5.40, with 20 hits and 10 walks in 25 innings (4.30 ERA in June).

But Grimm (6.04 ERA) has been a big part of it, struggling for much of the last six weeks, his velocity down and his pitches often up.

“I don’t know where those 2-3 mph are,” Maddon said. “The velocity is off a little bit, the command of the breaking ball is off a little bit. And that’s just something they’re going to have to iron out in the bullpen.”

The Warren Plan

Right-hander Adam Warren, who was optioned from the Cubs’ bullpen into the rotation at Class AAA Iowa to get stretched out for a spot start, makes his first Iowa start Saturday.

He’s expected to start twice at AAA, then make a start for the Cubs during the July 4-7 mini-homestand to give the five starters an extra day’s breather before the All-Star break.

Maddon said the team also is considering a similar spot start after the break.

Bullpen boost on near horizon?

Six-time All-Star closer Joe Nathan, who was signed to a big-league deal in April as he continued rehab from early 2015 Tommy John surgery, joined Class AA Tennessee on Thursday to start a minor-league rehab assignment.

Nathan, 41, has up to 30 days, barring a setback, to complete the assignment and join the Cubs’ bullpen – a timeline that could make him available just ahead of the July 25-28 set against the White Sox (against whom he has a career 2.39 ERA and 30 saves in 63 appearances).

Note: After an All-Star first half at advanced-A Myrtle Beach, second base prospect Ian Happ was promoted to Class AA Tennessee. The No. 9 overall pick in last year’s draft hit .296 with a .410 on-base percentage and seven homers for Myrtle Beach.