Pittsburgh right-hander Trevor Williams (12-9, 3.15 ERA) is at the top of his game, confident and looking to finish the season as one of baseball's hottest pitchers.
Miami right-hander Jeff Brigham (0-1, 9.00 ERA) will make his second major league start after nerves got the better of him in his debut.
Williams will make his 28th start of the season. He has allowed four runs in his past nine starts, has gone 5-2 with a 0.72 ERA in eight outings since the All-Star break, and has been the starter in eight of the Pirates' 14 shutout wins.
"I'm confident in my ability to pitch at the big league level and have success at the big league level," Williams said. "It's just a matter of executing pitches."
That and control are the crux of it.
"It's pitchability," Pittsburgh manager Clint Hurdle said. "It's flat-out pitch execution. He's a technician. He's hitting spots. He's throwing his fastball where he wants it, and he's changing speeds. And it's really hard to hit."
Williams hasn't faced the Marlins this year. He went 0-1 with an 11.57 ERA in two appearances (one start) in 2017.
Brigham was brought up from Triple-A New Orleans on Sept. 2 and made his major league debut that day against Toronto. He lasted only three innings, giving up three runs and four hits, with four walks and two strikeouts.
"I didn't stay within myself early," Brigham said. "It was a big day for me and definitely a good learning experience.
"My tempo was a little slow and I wasn't finishing my pitches -- wasn't trusting myself. I think that's one of the big issues there. A lot of pitches were left up."
Brigham was a combined 10-3 with a 2.36 ERA in three minor league levels before that debut, so Miami manager Don Mattingly suspects the rookie will be better when he calms down.
"Talking with (catcher) Chad (Wallach), he had never seen him all over the place like that," Mattingly said. "So, hopefully, it's one we get out of the way and next time out, he settles down and we get more like what we think we have. I think you can chalk that one up to (nerves)."
The teams are in different places, too, even though both are looking to next season rather than the postseason.
The Pirates (71-71) on Sunday will be aiming for a sweep, a sixth straight win and a chance to get back above .500. Miami (56-86) has lost eight of 11 and is in a race to avoid 100 losses.
One hitch for Pittsburgh is the loss of right fielder Gregory Polanco. He left Friday's game after an awkward slide into second.
The report Saturday was that he will miss the rest of the season because of a significant bone bruise on his left knee and a left shoulder injury. Polanco leads the team with 23 homers and 81 RBIs.