Darvish was slated to face Baltimore (50-42) for the first time since getting outpitched by Joe Saunders in last year's 5-1 wild-card loss, but he was scratched and placed on the disabled list Wednesday with a strained trapezius muscle in his throwing shoulder.
"At this stage, it's not something we're worried about," assistant general manager Thad Levine told MLB's official website. "If we sit him down for two weeks and miss one start, it's better for Darvish and he can hit the ground running in the second half. He is characterizing it as a fatigue type of deal more than anything."
Leading the majors with 157 strikeouts, Darvish is expected to be replaced by Wolf (1-1, 1.95 ERA). The right-hander has pitched out of the bullpen since beating Oakland 3-1 in his only career big league start May 22.
The 30-year-old Wolf, called up from Triple-A Round Rock earlier that day, allowed one run and three hits in five innings.
"I'm going to go out and do what I can do, throw strikes and get outs as quick as I can. I've been the long guy in the 'pen, so it's not that different," he said. "(The Orioles) have a good lineup. I just have to lock it in and give it all I got."
Baltimore had dropped five of six before winning 6-1 on Wednesday. Wei-Yin Chen returned from the DL to throw seven strong innings and Nolan Reimold went 2 for 4 with a three-run homer.
"Winning the ballgame is real huge," Chen said through an interpreter. "I'm healthy, and I'm back. I feel like I helped the team to win. Everything is for the Orioles."
Manny Machado had three more hits, bringing his total to 126 - second most in the majors behind Miguel Cabrera's 129. Machado is batting .403 with two homers, nine doubles and 10 RBIs in his last 15 home games.
The Orioles now turn to Miguel Gonzalez (6-3, 3.63), who has gone 4-1 with a 2.68 ERA in his last six starts. The right-hander allowed one run in six innings and was in line for the win Friday at Yankee Stadium before Jim Johnson blew the save in a 3-2 loss.
"Miguel was fortunate," manager Buck Showalter said of Gonzalez, who issued a career high-tying five walks. "But that's him. He's going to bend, but not break."
Gonzalez has won a career-high three straight home starts and has gone 7-0 with a 3.47 ERA in an 11-game stretch at Camden Yards dating to last year.
In his only appearance against Texas (53-38), Gonzalez surrendered four runs and eight hits in five innings of a 5-1 road loss Aug. 20.
He'll need to be careful against Adrian Beltre, who is batting .468 with six homers and 12 RBIs during a 12-game hitting streak. The slugging third baseman has recorded at least one hit in 14 of his last 15 regular-season games against the Orioles, going 26 for 63 (.413) with nine homers, 22 RBIs and 18 runs.
Despite an 0-for-4 effort with runners in scoring position Wednesday, the Rangers are hitting .357 in those situations during an 8-2 stretch on the road.