San Diego State lost star pitcher Stephen Strasburg late and withstood a ninth-inning rally in a 2-1 upset of No. 2-seed New Mexico Wednesday at the 2009 Conoco Mountain West Conference Baseball Championship at Lupton Stadium.

Strasburg suffered a lower back cramp in the bottom of the eighth inning and was forced out of the game. Aztec closer Addison Reed worked the final one and one-third innings, allowing one run and leaving the bases loaded to earn his national-leading 18th save in 18 chances this season.

"It just cramped up on me, obviously you sweat a little bit out here in Texas and I wasn't keeping enough fluids in me -- that's all," Strasburg said. "I was trying to fight through it but it was kind of at the point where it was cutting off my delivery."

Strasburg (13-0) left with two outs in the eighth inning after the final pitch of his only walk of the game. He threw one more pitch but winced in pain and was pulled from the game.

"I think he'll be fine and I don't think it's anything major," SDSU coach Tony Gwynn said. "We saw him wince and he said his back was tight."

Strasburg allowed just three singles and had six strikeouts, his first outing without double-digit strikeouts in at least seven innings of work since last year's MWC Tournament.

"We said let's don't let him have those 10-15 strikeouts, we're better than that," New Mexico coach Ray Birmingham said. "But at the same time we didn't smoke very many balls."

SDSU broke the scoreless game taking a 1-0 lead in the top of the sixth inning. Catcher Erik Castro ignited the inning with a single after Brandon Meredith walked. Following a fly out by Cory Vaughn, Mitch Blackburn lined a two-out RBI single to left.

In the top of the ninth, the Aztecs added a run on a wild pitch by New Mexico reliever Cole White.

"We don't have a wild pitch we're still out there," Birmingham said.

New Mexico left-handed starter John Hesketh (6-4) had rolled through the Aztecs lineup before the sixth. He retired the first nine batters in order and stranded the bases loaded in the fourth.

SDSU (39-19) advances to meet the winner of Wednesday night's TCU-Utah game Thursday at 7 p.m. CT.