Beavan, 23, went 4-0 with a 2.61 ERA in Triple-A Tacoma since being sent down a month ago. The Mariners need to fill the rotation spot of rookie Erasmo Ramirez, who is on the 15-day disabled list with a strained right elbow.
Beavan opened the season with the Mariners and went 3-6 with a 5.92 ERA in 12 starts. He was 5-6 with a 4.27 ERA in half a season with Seattle last year as a rookie.
The 6-foot-7 Texan beat Kansas City in his only appearance against the Royals on Sept. 9, allowing nine hits and three runs in 6 1/3 innings in a 7-3 victory at Safeco Field.
In his last Triple-A start, Beavan threw seven shutout innings with just two hits against Colorado Springs on Friday.
Delabar, 28, has been back and forth between Tacoma and Seattle three times this season. He's compiled a 2-1 record and 4.18 ERA in 32 1/3 innings over 30 games for the Mariners.
Ramirez is working out with the team on its current road trip, and the club hopes he's ready to go out on a Minor League rehab assignment sometime in the coming week.