It's the 23-year-old Thole's second stint with the big club this season, although he did not appear in a game during that May 10-15 stint. Thole hit .321 in 17 games with the Mets in September of last season and was batting .267 for the Bisons this year.
Barajas was out of the lineup on Thursday with what he described as stiffness. Henry Blanco made the start against Detroit and went 1-for-4.
After the game, manager Jerry Manuel said that Thole would probably get the start for Friday's series opener with the Twins.
Barajas, though, seemed determined to prove himself healthy enough to play by then.
"I know what major back pain feels like, and this is definitely not it," said Barajas, who has dealt with lower back injuries throughout his career. "If I come to feel where it's not going to limit me, I'll let [Manuel] know."
Valdes, meanwhile, was 2-2 with a 5.10 ERA and one save in 20 games for the Mets. He appeared in just three games since the start of June, and he had a 10.24 ERA over the last month. -- Tim Britton