Jackson left in the seventh inning of Thursday's game against the Padres with a back injury, Andrew Baggarly of The Athletic reports.

EDGE Analysis

Jackson signalled for the trainer after throwing ball four to Jackson Merrill, and Ryan Walker came in to close out the seventh. Jackson noted after the game that he felt his back tighten after his second to last pitch to Merrill, and the right-hander will undergo an MRI on Thursday night, per Shayna Rubin of the San Francisco Chronicle.