The move means that Wang will start Wednesday against the Marlins. According to Johnson, Detwiler took the news hard.
"It's a tough decision, and I think it's tough for the whole ballclub," Johnson said. "I'm reversing roles. It's easy for Detwiler to get warm. He is valuable, because I rank him up there with [Stephen Strasburg], Gio [Gonzalez] and [Jordan Zimmermann]. And I'm going to take care of him out of the bullpen."
Just a few weeks ago, it seemed like a no-brainer that Detwiler would remain in the rotation, but he has not pitched well in his last three starts and has seen his ERA climb from 2.10 to 3.88. It also didn't help that he threw 100 pitches in 4 1/3 innings against the Braves on Friday.
Wang, who started the season on the disabled list because of a strained left hamstring, made his season debut on Friday and pitched well, allowing one run in three innings to earn the win. Wang was slated to start the season as the fifth starter before he was injured in Spring Training.
Johnson said numbers were not the determining factor as to who stays in the rotation. Johnson needed to determine who would fit well in the bullpen.
Had Wang stayed in the bullpen, there was a good chance he would not be available to pitch often. Johnson has often said Wang was going to be treated as if he is a starter if he stayed in the bullpen, which would have meant pitching once every five days.
"You really don't want to tax him when he is just coming back fully from the two years when he was down from the major [shoulder] surgery," Johnson said about Wang. "It would be very hard for me to handle a [former] 19-game winner, who made a great comeback from arm surgery, to have him in the bullpen.
"Here is a guy who has been in pennant fights, too, and knows what the pressure is all about. So it's a good opportunity for him and for us, to have him be in the role he is accustomed to, and that's to start. It doesn't lessen the fact that I think Detwiler is one heck of a pitcher."
But Johnson said he is more concerned about his bullpen because of the injuries and inconsistencies the team has gone through this year.
With Henry Rodriguez no longer the closer, Johnson has decided that Tyler Clippard and Sean Burnett will split the closer's role until right-hander Drew Storen returns to action after the All-Star break.
"I'm more concerned -- not with the starters -- as I am with the bullpen," Johnson said. "I don't like to rearrange the roles. ... I don't like new tricks, but it's a talented bullpen. They are very good in different roles."