With Indians starters Justin Masterson and Ubaldo Jimenez coming off poor outings, Derek Lowe posting an 8.31 ERA in his last 10 starts and Josh Tomlin pitching to a 6.40 ERA in his last six games, McAllister has every opportunity to stay in the rotation if he continues his recent hot streak.
For the Orioles, who have two members of their Opening Day rotation pitching in Triple-A and another on the disabled list, Tillman is one of many green arms being counted on to make an impact.
In his two starts since being called up from Triple-A Norfolk, Tillman has had wildly differing results.
Against Seattle on July 4, Tillman showed off a new delivery and a mid-to-high 90s fastball, overpowering the Mariners to allow just two unearned runs in 8 1/3 innings.
But Tillman followed with an implosion on Monday against the Twins, allowing seven runs (only one earned) on five hits and two walks in just 2/3 of an inning as Minnesota pounded Baltimore 19-7.
"[It's] very frustrating," Tillman said. "I know what I'm capable of and I've been doing it for a while now [with Triple-A Norfolk]. It's disappointing not being able to make that adjustment and getting back down in the zone."
While Tillman has been up and down, McAllister has been extremely consistent during his latest stint in the Majors.
In four starts since his last call-up, McAllister is 3-0 with a 2.31 ERA.
He has notched 24 strikeouts in 23 1/3 innings, most recently tallying five while holding the Rays to one run on three hits and four walks in six innings on Monday.
McAllister knows what he has to do to stick in the Majors, long-term.
"If I do my job and pitch well, then I think that will happen," McAllister said. "I try not to think about that. I just want to go out and pitch well."
Orioles: O's add Quintanilla to infield
• The O's added Omar Quintanilla from the Mets on Friday in exchange for cash considerations, and the 30-year-old infielder is expected to be in Cleveland on Saturday.
With regular second basemen Robert Andino (shoulder) and Brian Roberts (hip) on the disabled list, Quintanilla could be a short-term answer at the position.
The O's have used utility men Ryan Flaherty and Steve Tolleson -- who have a combined .195 batting average this season -- at second base since Andino went on the disabled list.
• Jim Thome passed Sammy Sosa for seventh place on the all-time home run list with a fourth-inning solo shot on Friday.
Thome's 610 career blasts are 20 shy of Ken Griffey Jr. for sixth place.
• The Orioles are hitting .152 (12-for-79) with runners in scoring position in their last 10 games.
Indians: Allen makes Major League debut
• Only 13 months after being selected in the 23rd round of the 2011 First-Year Player Draft, right-hander Cody Allen was called up to the Majors on Friday and threw a scoreless inning in his debut.
Allen issued consecutive walks to load the bases after entering with one on and nobody out in the fourth, but retired the next three batters to escape the jam.
• Since moving to the leadoff spot, Shin-Soo Choo is batting .322, raising his average on the season from .235 to .297.
• Cleveland is 10-16 against the American League East this season.