WEST SACRAMENTO -- Gage Jump's shoulder never felt quite right.
Starting against the Mariners on Saturday at Sutter Health Park, the Athletics’ rookie left-hander felt stiffness and discomfort pretty much all evening -- in the bullpen, in the first inning and again in the second.
So when the A’s took the field for the third inning, Jump had departed the game, and right-hander Seth Johnson took the mound in his stead.
“I didn’t want to make it any worse,” Jump said.
The lefty’s early exit from Saturday’s 19-1 rout was the latest blow to an A’s rotation that will be without right-handers Luis Severino (right shoulder strain) and J.T. Ginn (right elbow impingement) for the rest of 2026.
After Sunday’s walk-off win, manager Mark Kotsay said Jump was diagnosed with left shoulder tendinitis and is likely headed to the 15-day injured list, which would end his season.
“We’ll make a determination on Tuesday,” Kotsay said.
Jump allowed five runs, all earned, in his two innings of work against Seattle. He threw 28 of his 44 pitches for strikes, allowing five hits -- including a pair of home runs -- while walking one and striking out two. Jump averaged just 93.7 mph on his four-seam fastball, 2.6 mph below his season average of 96.3 mph, and his fastest four-seamer of the night measured 94.9 mph.
The lefty’s most recent start came last Sunday against these same Mariners in Seattle, when he struck out seven over four innings of two-run ball. But on Saturday, he struggled from the outset, serving up a two-run homer to Dominic Canzone in the first inning and a three-run dinger to Randy Arozarena in the second.
Jump was MLB Pipeline’s No. 41 overall prospect when he was called up to make his big league debut, also against the Mariners in West Sacramento, back in May. He has a 5.47 ERA in 20 starts as a rookie, striking out 108 and walking 46 in 98 2/3 innings.
Along with lefties Jacob Lopez and Jeffrey Springs and righty Jack Perkins, Jump has been a fixture in the rotation for much of the season. He was impressive early on, posting a 2.04 ERA through his first six starts, but he has a 7.38 ERA in 11 outings since the All-Star break.
“I think he’s learned a lot here,” Kotsay said. “There’s been a lot of good starts, some bad ones. For him, this is the point of growing, learning, understanding the adjustments, the knowledge that he’s gained that will hopefully help him next year.”