The Arizona Diamondbacks starting rotation performed alarmingly poorly in its first 23 games of the season.

Then, an unexpected character — who is no longer even in the big leagues — stepped up, played “stopper” and things have been drastically better.

Indeed, before Mike Bolsinger’s 6.2-inning, scoreless outing on April 24 at Wrigley Field, the Diamondbacks staff was mired by a 7.15 earned run average and a collective record of 3-16.

You wouldn’t recognize the staff’s numbers if you saw them over the last 20 games. Or you at least wouldn’t attribute them to a group of 2014 Diamondbacks pitchers.

In 128.2 innings since April 23, Bolsinger, Wade Miley, Bronson Arroyo, Brandon McCarthy, Josh Collmenter and Chase Anderson have combined for a 3.08 ERA. They have garnered eight wins, four losses, a 1.104 walks-and-hits-per-innings-pitched (WHIP) clip and a 5.26 strikeouts-to-walk ratio.

Though allowing 23 home runs in their first 23 starts, Diamondbacks starters have allowed just 14 in their last 20 while putting together a 7.00 K/9 rate. They’re only walking 2.17 opposing hitters per nine innings in that span.

Arroyo made four of those starts and was the team’s best starting pitcher by a long shot in that stretch, allowing just three earned runs in 29.2 innings pitched for the Diamondbacks — good for a 0.91 ERA. On Tuesday, the veteran right-hander tossed a complete game against the Washington Nationals.

Another veteran right-hander, McCarthy, has been rock solid since April 23 as well. With the exception of a poor start against the Chicago White Sox, in which he allowed seven earned runs over 3.1 innings, the 30 year old has been borderline masterful. In his last four starts, McCarthy has a 3.55 ERA and 30 strikeouts spread over 25.1 innings pitched. If you remove his catastrophe in the southside of Chicago, the pitcher has a 1.23 ERA.

Two games after McCarthy’s implosion, rookie Chase Anderson made his major league debut at U.S. Cellular Field and was impressive, tossing 5.1 innings and allowing just a run on two hits while striking out six.

On Friday, Miley will take the mound against the visiting Los Angeles Dodgers.