The Washington Nationals placed left-hander PJ Poulin on the 15-day injured list on Sunday because of a left flexor strain.

The move was retroactive to Thursday. In a corresponding move, the Nationals signed free agent lefty Matt Krook. Washington transferred lefty Richard Lovelady (left triceps strain) from the 15- to 60-day IL to make room for Krook on the 40-man roster.

Poulin, who turns 30 on July 25, last pitched on July 11, allowing one hit and one walk with three strikeouts in 1 2/3 scoreless innings as the opener in a 4-2 home loss to the New York Yankees.

Poulin is 3-0 with three saves, a 2.70 ERA, 21 walks and 25 strikeouts in 36 2/3 innings over 35 games (11 starts) this season. Since making his major league debut last season, Poulin is 5-1 with four saves, a 3.08 ERA, 34 walks and 52 strikeouts in 61 1/3 innings over 63 games (11 starts).

The Nationals selected Krook, 31, off waivers from the Athletics on July 4 and designated him for assignment on July 12. He was granted free agency last Tuesday.

Krook was 0-1 with a 6.75 ERA, two walks and two strikeouts in 2 2/3 innings across three relief appearances for the Nationals. He was 0-0 with a 14.73 ERA in 3 2/3 innings for the Athletics earlier this season.

For his career, Krook is 0-1 with a 14.11 ERA, 14 walks and 15 strikeouts in 14 2/3 innings over 16 games with four teams since 2023.