Welcome to Camp MRI, where Mark Teixeira is the latest big name to light up like a Christmas Tree. Ten days after losing leading home run hitter Curtis Granderson until at least early May, the Yankees learned from team doctor Chris Ahmad they will be without Teixeira for 8-to-10 weeks with a strained ECU tendon in the right wrist. The first four weeks will consist of complete rest. “This ain’t good,’’ general manager Brian Cashman said while sitting in a wheelchair in the middle of the Yankees’ clubhouse with his broken leg and dislocated ankle in a cast — injuries suffered while skydiving earlier this week. No, it’s not. And simply because the 8-to-10-week time frame was applied to Teixeira’s injury doesn’t mean you can expect the switch-hitting first baseman back by the third week in May. Cashman said the injury was similar to Toronto’s Jose Bautista last year, and that is not good for the Yankees. Bautista was injured on July 17, played two games (Aug. 24-25) then had season-ending surgery. Unlike when they lost Granderson to a fractured right forearm, the Yankees don’t have depth to cover Teixeira’s loss. The cleanest way to replace Teixeira is to shift Kevin Youkilis from third to first, where he has played more games and won a Gold Glove in 2007. Youkilis has played 607 at first base, 442 at third. Moving Youkilis likely would force the Yankees to move Eduardo Nunez from Derek Jeter’s backup at short to third, a switch the Yankees are leery of doing because they believe moving Nunez around last year led to his fielding problems.