The Twins starting rotation has only three concrete members at the moment, with what-ifs and we'll-sees filling out their plans for the other two spots.

And that's the stable side of the pitching staff.

The bullpen, one of the reasons for surprise and optimism though the first four weeks of the season, melted down during last week's six-game homestand, with Boston's 10-run ninth inning Sunday the final inferno. The Twins arrived home a week ago with a 3.75 bullpen ERA, sixth-best in the American League. They left for Chicago on Monday toting a 4.90 mark — worse than even their 4.63 ERA that ranked dead last in the AL in 2016.

"Sometimes you're going to take it on the chin. It's not something you want to have happen," said Twins manager Paul Molitor, trying to put the ugliness behind him. "Sometimes we have to give [opposing] hitters a little credit, too."

That might be, but the sudden downturn, even if overstated by that big number Sunday, has to worry the Twins. Molitor was forced to use a franchise-record 23 relief pitchers in 2016, including infielder Eduardo Escobar, and the constant shuffle gave the season a chaotic feel.

That feel returned last weekend. Michael Tonkin, who surrendered a hit in all nine of his appearances this year and at least one run in six of them, was designated for assignment. Nick Tepesch, called up as a long reliever but never used, was suddenly switched to the rotation. Drew Rucinski was added and Justin Haley was activated, but they have 14 games of big-league experience between then.

"We have been scrambling the whole homestand. A lot of transactions and people getting shuffled around," Molitor said. "The dynamics of your 'pen change fairly regularly throughout the year. Obviously, these guys are going to get a chance to regroup and come back."

Even the front of the bullpen became vulnerable when the Red Sox arrived. Closer Brandon Kintzler failed to convert a save for the first time this season Friday, though the hits off him were more well-placed than well-struck. Matt Belisle, who had 11 scoreless appearances among his 14 games, was the chief victim Sunday, giving up six runs. Taylor Rogers gave up a run Sunday, too, while recording only one out. And Ryan Pressly was rescued by a double play from surrendering a run for the third consecutive outing.

"This has definitely been the worst month of my career overall — majors, minors, probably all the way back to when I started playing baseball," Pressly said. "I'm just trying to power through it, stay mentally strong enough to keep myself going. I know my stuff plays up here. It's just a matter of throwing strikes."

The good news? Help is on the horizon. By jettisoning Tonkin and demoting Kyle Gibson last week, Chief Baseball Officer Derek Falvey and General Manager Thad Levine demonstrated a willingness to hold players accountable for subpar performance, and the Twins' leadership has some bullpen prospects, gathered by the previous regime of Terry Ryan, to promote when ready.

Sidearmer Trevor Hildenberger has struck out 11 batters in 9 ⅔ innings for Class AAA Rochester, albeit with 10 hits, too. Hard-throwing J.T. Chargois is recovering from an elbow impingement but could get another shot once he shows he's healthy. Alex Wimmers has converted his past three save situations for the Red Wings, though he is battling control problems.

And at Class AA Chattanooga, four of the organization's top bullpen prospects are making cases to help the Twins soon. A solo home run is the lone run Nick Burdi has given up in nine games; he has struck out 13 in 10 innings. Luke Bard has 24 strikeouts in 15 innings, with only five walks. John Curtiss hasn't given up an earned run in 11 ⅓ innings, with 14 strikeouts and four saves. And Mason Melotakis, scouts report, is most dominant of all: 13 ⅔ innings, five hits and a 0.00 ERA.

"There will be some tough decisions down the road. But you want those type of decisions — [sorting] through talented guys who can help," Molitor said. "When it happens, who can say? My job is to stay in the present and try to win with the guys who are here."