Doug Mathis, who was recalled from Triple-A Oklahoma in the wake of Millwood's strained right groin, seemed like the plausible move, but the hurler has shown promise in his brief Major League tenure and could slide into a middle-relief role.
"It's a possibility, but we certainly are going to do what we feel is best to help us," manager Ron Washington said. "If that means putting [Mathis] in the bullpen, that's where we are going to put him. If the decision is made that [that a move to the bullpen would hurt him as a starter] then we won't."
Mathis received his promotion on May 11, when Millwood was sent to the DL, and has since seen action in five games, three of which have been in relief.
Millwood -- who missed a substantial amount of time in May last season as well -- was 2-3 with a 4.88 ERA in his first nine starts before the strain. The club could also elect to keep Mathis to make sure there are no residual effects from the injury, as Millwood re-aggravated his strained hamstring immediately upon his return last year.
Either way, Washington said the move is "not a done deal," and the club will likely mull over the decision until Millwood's activation on Friday.
"We haven't made that decision yet," the skipper said. "Right now, [Mathis] is still here."
The right-hander entered Tuesday with a 5.56 ERA in 11 1/3 innings pitched. He earned his first win on May 12 with a scoreless inning against the Mariners, making him the first Rangers reliever ever to record a "W" in his Major League debut.
As a starter with Oklahoma, Mathis was 5-0 with a 3.55 ERA in seven games before getting the call up to the big leagues.
In other pitching news, Washington confirmed that Thursday's off-day would not throw off the club's scheduled rotation. Instead, each starter will get an extra day of rest in between appearances.
Brittany Ghiroli is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.