Diamond has struggled mightily this season, battling inconsistency and an inability to provide quality starts. In 20 outings this season he has a 5-10 record with a 5.52 ERA. He pitched at least six innings on only seven occasions, including one seven-inning start.
The left-hander's five-inning outing on Thursday became the catalyst for change. He gave up seven runs, six earned, on nine hits and three walks, one intentional. He managed only one strikeout as he took the loss.
"He's fighting it and needs to regroup," Twins manager Ron Gardenhire said. "He knows that and said it himself. He has a lot of pressure up here, and he puts a lot of that on himself. He wants to do well."
Diamond didn't hide his feelings about the move, but also noted that the game is a business.
"I have to face the facts," Diamond said. "I just haven't been pitching well. I haven't been executing. I haven't been putting hitters away. I just haven't stopped the bleeding. I just really haven't been giving our team the best chance to win. If you're not impacting the team or contributing at all, then you don't deserve to be here. So right now I need to go down to Triple-A and figure some things out and hopefully come back."
With how he has fared this season, Diamond admitted he was afraid of this move happening, but is going to use the opportunity to regroup.
"I just need to get back to being aggressive and clear my head and reset a little bit," Diamond said. "I think right now I'm trying to do a lot. I was fearful of this actually happening, and so I think because of it I was just trying to do too much. Hopefully this just helps reset things and gets me back to the basics of just attacking hitters and throwing strikes."
While the Twins won't announce who will be filling Diamond's spot on the roster, most bets are on left-hander Andrew Albers.
Albers, 27, has fared well at Triple-A Rochester this year, posting a 2.86 ERA with 116 strikeouts and 32 walks in 132 1/3 innings. The left-hander was also solid on Wednesday, giving up two runs on five hits over eight innings against Lehigh Valley.
Albers isn't currently on the 40-man roster, but the Twins have an open spot after trading catcher Drew Butera to the Dodgers on Wednesday.
Much like Diamond, Hicks is hoping to reset and find some confidence with the move.
"I'll be able to just relax and have fun playing the game and get that competitive edge back," Hicks said.
Since the All-Star break, Hicks has just seven hits in 43 at-bats for a .163 average. While his defense has remained top-notch, Gardenhire said his swing "isn't where it needs to be."
"Things just haven't been happening," Hicks said. "In this game that happens. I feel like I lay down a perfect bunt [on Wednesday] and the guy throws me out -- it's just the nature of the game. You can still do everything perfect and still get out."
Arcia will return to the Twins to fill in the outfield. In his latest stint in Rochester -- July 19 to July 31 -- Arcia was 15-for-40 for a .375 average and a .490 on base percentage. He also hit four home runs in 13 games.
"Arcia went down and was swinging pretty good. He's fun to watch," Gardenhire said. "He'll bring some life to us hopefully, and put some swings on and hopefully help us drive in some runs."
Kelly Erickson is an associate reporter for MLB.com.