The Rangers, who have the third-worst starting rotation ERA in the majors, on Monday sent out the pitcher with the lowest ERA among the 10 who have started for them this season.

In order to prep for the return of Martin Perez to the rotation, Austin Bibens-Dirkx, who has a 3.71 ERA for six starts, was optioned to Triple-A Round Rock. Bibens-Dirkx started Sunday and wasn't going to start again before the All-Star break. By sending Bibens-Dirkx out Monday, he could be recalled as early as the end of the All-Star break on July 19.

The move was necessitated by the arrival of reliever Cory Gearrin, acquired in a trade with San Francisco on Sunday. The Rangers also acquired outfielder Austin Jackson but have told the Denton native not to rush to join the club as there is no real playing time. The Rangers will either add Jackson to the roster by Wednesday, trade him or designate him for assignment. If he does join the team, it will require another move on the 25-man roster.

It was the easiest and simplest move for the Rangers to make to accommodate the return of Perez, who has missed more than two months while dealing with inflammation in the ulnar collateral nerve in his right (non-throwing) elbow.

Perez is likely to join the rotation Saturday in Baltimore.

Bibens-Dirkx pitched 5.1 shutout innings against Detroit on Sunday, allowing three hits. He has allowed one or no runs in three of his past four starts, though those three starts came against Kansas City, San Diego and Detroit, all teams at least 10 games under .500. In the other start, against AL West-leading Houston, he allowed nine hits and five runs in six innings.

Briefly: 2B Josh Atlmann, 24, was named the Class A Carolina League Player of the Month for June. He hit .323 for Class A Down East and led the league with a 1.183 OPS. ... OF Scott Heineman, who began the season at Double-A Frisco, has been added to the Pacific Coast League team for Wednesday's Triple-A All-Star Game in Columbus, Ohio. Heineman entered the All-Star break with a 10-game hitting streak and a slash line of .303/.363/.450/.812 since joining the Express. ...Rougned Odor played his 39th consecutive error-free game Monday, establishing a new career best. Odor had played 38 straight games without an error from Sept. 20, 2014 through April 11, 2015.

Twitter: @EvanPGrant