The Twins also have offered free-agent right-hander Ervin Santana a three-year deal, according to various reports, although it appears unlikely he'll land in Minnesota. Santana is reportedly more interested in signing a one-year deal to re-establish his value for next season.
The Twins remain more inclined to stay in-house for that fifth spot, and assistant general manager Rob Antony believes there isn't a clear-cut front-runner just yet.
"When it comes to starters, until they're stretched out a little more and go four or five innings, it's hard to go off an inning or two," Antony said. "Because if a guy goes out there and has one good inning, and then his next start, he has one good one and one bad one, what did you really figure out? They all have had their moments, and they've all had things they didn't do well. So I don't think anybody has separated themselves early on."
Deduno appears to be the slight favorite to claim the final spot in the rotation, given his success last season, when he posted a 3.83 ERA with 67 strikeouts and 41 walks in 108 innings.
Deduno ended the year on the disabled list after undergoing arthroscopic shoulder surgery in late September, but he has looked healthy and effective again this spring. The 30-year-old has a 1.35 ERA in three Grapefruit League outings, with six strikeouts and three walks in 6 2/3 innings.
Twins manager Ron Gardenhire also gave Deduno a ringing endorsement after he threw three scoreless innings against the Phillies on Sunday. He didn't quite hand Deduno a spot in the rotation, but Gardenhire said he'd like him on his roster this season -- whether it be as a starter or a reliever.
"He's filthy," Gardenhire said. "Coming out of the 'pen, whatever, I like the guy and would like him on my staff. I would love to have this guy on my staff, because he has great makeup and he can help us win baseball games. One way or another, he can help us, starting or relieving."
Worley still has upside, as he still has youth on his side -- at 26, he's four years younger than Deduno -- and posted an impressive 3.50 ERA in his three seasons in Philadelphia before being traded to Minnesota before last season. But Worley really struggled in 2013, as he went from being the club's Opening Day starter to being optioned to Triple-A Rochester after putting up a 7.21 ERA in 10 starts.
Like Deduno, Worley's campaign also ended with shoulder problems, but he's also healthy this spring and is about 25 pounds lighter than last season. He looked sharp in his first Grapefruit League outing but was roughed up by the Pirates on Sunday, when he lasted just 1 1/3 innings and gave up five runs on seven hits and a walk.
It was just one subpar outing, and Worley's not fully stretched out yet, so he's hardly out of the running. But Gardenhire did say he wants to see more from Worley.
"They blooped some balls in and had some choppers in the infield, and it's early in Spring Training, but we want to see better than that." Gardenhire said. "But he has a better angle and the ball is going down better."
Diamond, 27, is also trying to bounce back after a rough 2013, as he went from posting a 3.54 ERA in 27 starts as a rookie to a 5.43 ERA in 24 starts last year. He started the year on the disabled list after undergoing elbow surgery during the offseason, and couldn't replicate his success from the previous season.
Diamond has made two Grapefruit League appearances so far, giving up six runs (two earned) on six hits over four innings. He wasn't helped by an error in his last outing that led to four unearned runs scoring in one inning, but he also couldn't limit the damage.
As the lone left-handed candidate for the rotation, Diamond knows that alone won't give him the edge, as he has to show the coaching staff he can locate the ball like he did his rookie season.
Gibson, 26, has looked solid this spring, as he's yet to give up an earned run in five innings, with two strikeouts and a walk. He got his first taste of the Majors last season, but he posted a 6.53 ERA in 10 starts. The Twins still have high hopes for Gibson, but he might be on the outside looking in at the end of camp, if only because he has Minor League options left.
Gardenhire said he's simply looking for the best candidate to emerge this spring to take that final spot in the rotation.
"[We] have roster issues, guys that are out of options, but I think you take the best player," Gardenhire said. "Best pitcher. That's what we have to do. We've lost enough. Now it's time to take the best pitchers."