Cards begin two game set with Astros at Houston.
The Astros and Cardinals still aren't used to life without each other as division rivals.
The former National League Central opponents square off in Houston on Tuesday, briefly rekindling their history with a two-game series.
Once playoff combatants for the National League crown in back-to-back years in 2004-05, they're now Interleague foes.
Despite the separate leagues, a lot has remained the same from their more recent history.
The Cardinals are 47-29 and sit atop the NL Central, perhaps primed for another deep playoff run, while the Astros got off to a slow start in the American League West, where they sit in last place.
But Houston has shown itself considerably better of late, going 14-11 since May 29 and winning seven of its last 11, some in thrilling fashion.
There was a walk-off homer on Thursday against another former NL Central rival in the Brewers and a ninth-inning suicide squeeze against the Cubs on Saturday.
Astros manager Bo Porter said he's been using those late-game situations to try and manage more to his roster's strengths during the last month.
Houston originally planned to start left-hander Erik Bedard, but righty Lucas Harrell will get the nod instead.
Bedard will oppose the Cardinals' Lance Lynn on Wednesday.
Harrell has hit a groove in June, going 1-1 with a 1.73 ERA in four starts.
In that span, the righty has struck out 17 batters and walked four across 26 innings.
Only Ervin Santana of the Royals has been better in June among AL pitchers with at least 20 innings.
Harrell, who struggled in April, has now allowed three earned runs or fewer in seven of his last nine starts.
After posting a 3.76 ERA over 193 2/3 innings last year, his first full season in the Majors, the right-hander is again looking like a prominent starter for a rebuilding team.
The Astros went 5-2 in a seven-game run at Minute Maid Park last week.
St. Louis hopes to stunt that home cooking with righty Jake Westbrook, who was brilliant over seven innings of scoreless work in a 4-1 win against the Cubs on Wednesday.
The Cardinals have recently dominated the matchup with Houston, claiming 21 of the last 30 games and five of the last six season series before the Astros changed leagues prior to this year.
For St. Louis, the turn of the schedule toward American League parks should give Matt Adams the chance to get some playing time at designated hitter.
The Cardinals may not have a fifth starter in the rotation after Tyler Lyons was optioned back to Triple-A Memphis, but they may not need one soon.
With three off-days between Monday and July 8, Matheny has ample room to maneuver his rotation to fit.
This is Houston's third straight series against former NL Central rivals, having played the Brewers and Cubs in three-game sets over the last week.
The Cardinals recalled righty reliever Michael Blazek in place of Lyons on Saturday.
That makes 10 rookie pitchers to appear on St. Louis' active roster this season.