The Texas Rangers were swept in Oakland after an 8-1 matinee loss on Wednesday, but rotation help is on the horizon. Yu Darvish worked five strong innings for Double-A Frisco on Tuesday and is now slated for what is shaping up to be his final rehab start since undergoing Tommy John surgery last year.

In a press release, the Rangers offered up the following details:

Texas Rangers pitcher Yu Darvish is scheduled to make his fifth start on injury rehab assignment on Sunday, May 22 when he will pitch for the Frisco RoughRiders versus the San Antonio Missions at Dr Pepper Ballpark in Frisco. First pitch is at 4:05 p.m. and Darvish is scheduled for 6.0 innings or 90 pitches.

Once a pitcher has proven he’s OK to get through six innings and in the range of 90 pitches without a setback, he’s ready to join the big-league rotation.

Darvish’s performances thus far in the process have been very encouraging, too. On Tuesday, he allowed only three hits (all singles) and an unearned run while striking out six and walking only one in five innings. In four rehab starts, he has a 1.29 ERA, 0.79 WHIP and 15 strikeouts against five walks in 14 innings. He’s overall been pretty efficient with pitches per inning, too, throwing strikes on 62 percent of his pitches.

Should Darvish emerge from Sunday’s outing without setback, he’d be ready to pitch Friday, May 27 against Pittsburgh on normal rest or could take the ball either Saturday or Sunday with an extra day or two buffer.

With A.J. Griffin on the DL, Darvish will slide into the Rangers’ rotation in place of spot-holder Cesar Ramos. Once Griffin is back, however, it looks like the Rangers will have to decide which one of Martin Perez (1-4, 3.48), Colby Lewis (2-0, 3.12), Derek Holland (3-3, 5.63) and Griffin (3-0, 2.94) loses a rotation spot behind Cole Hamels and Darvish.