"Things are going well, I'm feeling good and then it's like, 'Shoot, you're kidding me,'" Bass said after the Padres fell to the Rangers, 4-2, at Petco Park.
Bass -- who allowed one run over five innings and had thrown 60 pitches to that point -- indicated that his shoulder started bothering him only in that last inning.
"I was hoping it went away, but it didn't," Bass said.
The Padres have an off-day on Thursday, though Bass will come to the ballpark to meet with team doctor, Heinz Hoenecke.
"We'll hope it's just that -- inflammation," Padres manager Bud Black said. "There's no immediate plan. We'll have to let this play out."
Bass, who entered the game having allowed 26 earned runs in his last 26 1/3 innings, was off to a good start against the Rangers in the final game of a three-game series at Petco Park.
Even with the bat.
Bass singled down the first-base line in his first at-bat of the game, driving in two runs for a 2-0 lead.
On a pitching staff decimated with injuries this season, Bass has been one of the most durable arms on the staff. His start on Wednesday was his 14th of the season. He started the season as the long reliever, but moved into the rotation because of injuries.
It's far too soon to know if Bass will need a stint on the disabled list, though he doesn't think that he will. The Padres, undoubtedly, are hoping he doesn't.
They already have five starting pitchers on the disabled list -- Tim Stauffer (strained right elbow), Dustin Moseley (strained right shoulder), Cory Luebke (reconstructive elbow surgery), Joe Wieland (strained right elbow) and Eric Stults (strained left lat muscle).