The Nationals paved the way for the return of left-hander Gio Gonzalez by optioning right-handed starter Blake Treinen to Triple-A Syracuse on Friday.
Treinen went 0-2 with a 2.89 ERA in three starts in his most recent stint. Overall, he is 0-3 with a 2.80 ERA in eight major league games, including four starts over 30 1/3 innings.
In Thursday's 7-1 loss to the Giants, Treinen lasted five innings, allowed five hits, two runs, three walks and struck out two. He struggled a bit with his command in the game, as he issued his first free passes since May 22.
The team called up left-hander Xavier Cedeno. The 27-year-old pitched 1 1/3 scoreless innings against the Dodgers on April 21, his lone appearance this season with the Nationals. In 13 appearances with Syracuse, Cedeno is 2-0 with a 1.23 ERA in 14 2/3 innings. He has 20 strikeouts and only three walks.
Cedeno has arrived in St. Louis and has joined the team at Busch Stadium.
Gonzalez tossed four innings Thursday for high Single-A Potomac, striking out seven batters and allowing one run. He has been on the disabled list with left shoulder inflammation since May 18. He is expected to start Wednesday's home game against the Astros.