Teheran (3-4, 3.67 ERA) will be opposed by St. Louis right-hander Jack Flaherty (4-3, 4.19) in the finale of a three-game set.
The teams have split the first two games of the series, with the Cardinals winning on Saturday with a four-run eighth inning capped by Jedd Gyorko's three-run pinch-hit homer.
Teheran struggled in April, going 2-3 with a 5.35 ERA and causing speculation that the veteran might even be moved to make way for some of the team's young pitching prospects. But the right-hander has put a stop to such talk with his performances in May. Through four starts this month, Teheran is 1-0 with a 0.79 ERA. He has not allowed more than one run or three hits in any of his appearances.
In his last start, Teheran pitched 5 2/3 innings and allowed one run against the San Francisco Giants. He received no decision in a 4-3 loss.
"He made big pitches. He did his job," Atlanta manager Brian Snitker said.
Teheran has historically pitched well against the Cardinals. He is 3-3 with a 2.77 ERA in seven career starts against St. Louis. He has fanned 35 batters in 39 innings and allowed only four homers. He started at home against the Cardinals on May 16 and threw five scoreless innings, striking out four.
Flaherty has pitched reasonably well in May, but not as effectively as he did in April, when he went 3-1 with a 3.38 ERA. In four starts this month, he's 1-2 with a 4.37 ERA; he's pitched at least five innings each time and not allowed more than three earned runs in any appearance.
In Flaherty's last start on May 19, he threw six innings and allowed two runs on four hits against the Texas Rangers. He walked two -- three fewer than his previous start - and struck out six but received no decision in a 5-4 loss.
Flaherty beat the Braves on May 14 when he benefited from the Cardinals' 14-run outburst. On that day, he worked six innings and allowed three runs on three hits with six strikeouts. That evened his career record against Atlanta to 1-1 and lowered his ERA against the Braves to 6.75 in two starts.
Flaherty's place in the rotation seems secure, although other spots remain in flux. There is concern about the viability of Adam Wainright, and on Friday, the Cardinals announced that Michael Wacha has been moved to the bullpen. Wacha allowed seven runs (six earned) in 4 2/3 innings against Kansas City in his last start, pushing his ERA to 5.59.
"Speaking of Michael, clearly a tough decision," St. Louis manager Mike Shildt said. "We can't be naive to the fact that it's a result-oriented business, and the timing of him pitching better but being on a string of inconsistent outings affected the decision.
"I think there's a route back for him (to get back into the rotation), but he's got to go get some of the things we talked about more consistent."
The Cardinals are expected to promote another starter from Triple-A Memphis, possibly Daniel Ponce de Leon or Jake Woodford, to take Wacha's next turn on Wednesday.
--Field Level Media