The St. Louis Cardinals sophomore takes on the Marlins freshman Saturday at Busch Stadium with both 23-year-olds looking to overcome mounting struggles.
Miller (7-7, 4.10 ERA) has for the most part struggled since the middle of May, but he's been awful in his last three starts with two losses and an 8.16 ERA.
In Sunday's 6-0 road loss to the Los Angeles Dodgers, the right-hander gave up six runs and seven hits in five innings. He's walked 15 during a four-start winless streak.
"It's just frustrating when you give up runs and give up those big innings," said Miller, who has surrendered innings of four and three runs over his last two starts. "You give them a lot of momentum."
Miller will get a fresh start with his first crack at Miami, though the only batter he's faced in its lineup, Garrett Jones, has crushed him to the tune of 7 for 10 with two home runs and two doubles.
Heaney (0-3, 5.29), ranked as the Marlins' top prospect by MLB.com, had a promising debut June 19, but he allowed nine runs in 11 innings over his next two starts. The left-hander yielded four runs and eight hits over six innings of Sunday's 4-3 loss to Oakland.
"He looked more comfortable to me today," manager Mike Redmond told MLB's official website. "He was pounding the strike zone with the fastball. You could tell by the swings. I think that will continue as he gets more and more starts. He's going to be fine. He's got good stuff. I like his poise out there. I like his demeanor, the way he competes."
His teammates could certainly help by upping his run-support average from its current 2.12 standing.
"I feel like every time out, I've gotten better," Heaney said. "Hopefully, I can have one where I'm taking a lot more positives and celebrating a win."
The Cardinals (47-40) did that in Friday's 3-2 series opener for their third straight victory, a streak in which their starters have a 0.47 ERA. It came at a good time after the lineup had produced just four runs in five games preceding the winning streak.
Yadier Molina went 2 for 2 with a run-scoring double and is 8 for 16 over five games, a stretch his manager considers deserved after he'd lined into some hard outs recently.
"We've seen Yaddy hit a lot of balls that way that don't find the grass and he finally found one that did," said Mike Matheny, who also has leadoff hitter Matt Carpenter batting .412 on a nine-game hitting streak.
The Marlins (41-45) have lost six straight in St. Louis with 15 runs scored and a .207 average. They rallied from 3-0 down in the ninth Friday before Casey McGehee grounded into a game-ending double play. The third baseman, however, went 2 for 4 and is batting .348 on an 11-game hitting streak. He's also riding an 18-game road streak for a .418 average.
Miami has dropped six of eight with its last four losses coming in one-run contests.
The Marlins placed second baseman Derek Dietrich on the 15-day disabled list Friday after he suffered a strained right wrist Tuesday.
Cardinals outfielder Allen Craig has been out of the lineup for consecutive games as Matheny tries to work left-handed rookie Oscar Taveras into regular at-bats. Craig, a right-handed hitter, is 2 for 18 over his last five games but is likely to start against the Marlins lefty.