Austin Nola's frustrating stop-and-start 2021 season has reached another "stop."

The Padres will place their starting catcher on the injured list Friday, manager Jayce Tingler said, after Nola was diagnosed with what Tingler called "a slight knee sprain."

Nola has played in only 18 games this season after missing most of April because of a fractured finger in his left hand. Tingler said he was optimistic that Nola would be back on the field in a couple weeks.

"He's probably more frustrated with it," Tingler said. "We got the news, and we were somewhat relieved that it wasn't anything worse. But he's a competitor, and it frustrates him not to get in there and get with the guys -- especially [because] he was starting to find his rhythm and timing."

Nola is hitting just .217 this season with a .699 OPS, but as Tingler noted, he'd begun to find a groove at the plate. In his past 10 games, Nola was hitting .286/.444/.429.

With Nola headed for the injured list, it's unclear who will take his place ahead of the Padres' series in Houston this weekend. When Nola missed the season's first four weeks, Luis Campusano -- the team's No. 3 prospect, per MLB Pipeline -- took over. But Campusano struggled, and the Padres clearly want to see him get further seasoning in the Minors.

"Short answer: I don't know yet," Tingler said. "The one thing I will be committed to is not overtaxing Victor [Caratini]."

Here's where it's worth praising Caratini for the job he's done while handling a surprisingly hefty portion of the catching duties. When the Padres traded for Caratini, they envisioned him as a personal catcher for Yu Darvish and serving as Nola's backup.

Instead, Caratini has played in 36 of the team's 51 games, drawing rave reviews for his defense. He's also reaching base at a .331 clip, with a handful of clutch hits this season -- including a game-winning single in the 10th inning on Wednesday in Milwaukee.