General manager Brian Cashman has not been told by the Yankees medical staff that Mark Teixeira’s strained right wrist might require surgery. Yet because Toronto’s Mark DeRosa and Jose Bautista needed surgery to repair tendons in the same area, Teixeira was instructed by the doctors to rest for four weeks or surgery could be in play. “They have never mentioned surgery,’’ Cashman said after Saturday’s 2-1 exhibition loss to the Braves at Steinbrenner Field. “I guess if his rehab goes badly ... but they never mentioned it.” DeRosa had a torn sheath, something Cashman says Teixeira doesn’t have. “The sheath is fine,’’ said Cashman, who estimates the switch-hitting first baseman will return in mid-May if the rehab goes well. Cashman isn’t optimistic about making a deal to acquire a corner infielder to replace Teixeira even though the in-house candidates at first base — Dan Johnson and Juan Rivera — don’t instill a lot of confidence.