Carpenter has dominated the Washington franchise in the past, going 5-0 with a 3.49 ERA in seven career starts against the former Montreal Expos. He went 2-0 with a 1.69 ERA in two starts against the Expos last season.
The veteran right-hander is 3-0 with a 2.70 ERA over his last three starts. Carpenter allowed one run and four hits over seven innings in a 4-2 win over Pittsburgh on Monday.
Carpenter is 4-2 with a 4.17 ERA in six home starts this season. The Cardinals are 8-2 in his starts overall.
Hernandez will try to help halt Washington’s season-high five-game losing streak. He is 6-0 with a 3.60 ERA over his last seven starts.
The veteran right-hander missed a chance at winning his seventh straight start as he did not receive a decision in a 4-3 loss at Cincinnati on Tuesday, allowing three runs and six hits over seven innings.
Hernandez is bidding to win five games in a month for the first time in his career. He is on his longest winning streak since a nine-game run from June 28-Sept. 6, 1997.
St. Louis is bidding for an eighth straight home win after a 3-1 victory Saturday. Yadier Molina hit a two-run homer and Jim Edmonds also connected to support starter Jeff Suppan, who pitched seven solid innings.
Edmonds had been in a 1-for-14 slump before going 4-for-7 in the first two games of this series. He has six of his 31 RBIs over the last three games.
The Nationals are 1-7 heading into the finale of a nine-game road trip. Washington has scored a total of 13 runs during its losing streak.