UPDATE (6/20): Zambrano has a minor strain in his right shoulder but no major structural damage, a team spokesman said after the Cubs' 4-3 victory over the Chicago White Sox on Friday. Zambrano underwent an MRI arthrogram, a test in which dye is injected into the troubled area to provide a more detailed look, at Northwestern Memorial Hospital on Friday and headed home. He will meet with the trainers and coaching staff on Saturday. Cubs manager Lou Piniella has said Zambrano will miss his scheduled start against Baltimore on Tuesday. But the plan beyond that is unclear.

The Cubs' season could hinge on the outcome of an MRI of Carlos Zambrano's pitching shoulder today in Chicago before the team finishes a painful road trip tonight against the Tampa Bay Rays.

The player the Cubs can least afford to lose left Wednesday night's game with two outs in the seventh inning after feeling pain in his shoulder near the end of his start at Tropicana Field, according to the Chicago Sun-Times.

"There was a funny pitch that I felt something in my arm, and then the last pitch that I threw in the game, I dropped my arm a lot because I couldn't go back over the top with my arm," said Zambrano (8-3), who was charged with the 5-4 loss to the Rays.

Zambrano is 2-2 with a 4.67 ERA in seven starts since waking with shoulder stiffness last month, walking three or more batters in five of the seven starts. He was 6-1 with a 2.03 ERA before that.

He's scheduled to fly this morning to Chicago to meet with team doctors and undergo an MRI.

"We hope for the best. That's all we can do," manager Lou Piniella said.