Anthony Fenech

Detroit Free Press

LAKELAND, Fla. -- Bruce Rondon improved off of the field this spring. It was evident in the way he went about his business, Detroit Tigers manager Brad Ausmus said throughout training camp, from the way he carried himself in the clubhouse to the way he prepared himself between appearances.

But that improvement wasn’t evident enough on the mound to earn a spot on the Opening Day roster. The right-handed reliever was optioned to Triple-A Toledo this afternoon.

In nine games this spring, he allowed six runs on 10 hits. He struck out 12 and walked three.

“He’s been a little up and down,” Ausmus said after Sunday’s loss to the Houston Astros, in which Rondon allowed four runs on three hits -- including two home runs -- and was unable to escape the seventh inning. “He’s been real good on days and scuffled on days.”

In any given appearance, Rondon would flash the potential that has tantalized the Tigers since 2013, when they anointed him the closer coming into spring training.

The competition for the final few bullpen spots -- which depends, in large part, on the health of lefty Blaine Hardy, who didn’t throw this weekend -- cleared up not only with today's Rondon’s option but also with the unconditional release of righty Bobby Parnell.

Parnell, 31, signed a minor league deal last month. He, like Rondon, was up-and-down, allowing nine runs on 14 hits in 8 1/3 innings.

Parnell and third baseman Casey McGehee, also granted his unconditional release, needed to be added to the Tigers’ 40-man roster by Tuesday or could have opted out of their contracts or been given a $100,000 roster bonus to accept a minor league assignment.

Asked whether there was a chance Parnell might come back, Ausmus said: “Yeah ... there’s a chance.”

McGehee, 33, hit .316 in 20 games this spring.

“We kind of knew what he was,” Ausmus said of McGehee. “He has a little bit of a track record. Kind of had up-and-down seasons at the major league level, but at times he’s been a very productive hitter. But I think he’s kind of a baseball player, you can see by the makeup. He knows what he’s doing at third base. He’s got experience there. He was kind of what we thought he would be, just a situation where we don’t really have a slot for him.”

They could stay with the team by signing a new deal, but today’s release also makes them free agents.

Briefly: Catcher Bryan Holaday originally was listed in the lineup for Monday’s game but didn’t make the trip from Lakeland. Ausmus said Holaday was getting his thumb checked out. Holaday caught a pitch awkwardly Saturday.

Contact Anthony Fenech: afenech@freepress.com. Follow him on Twitter @anthonyfenech.