Hamels earned a five-game ban stemming from the incident, and as a result, he'll throw in the series finale against San Diego after flipping spots in the rotation with Roy Halladay.
Hamels faces the Padres' Jeff Suppan, who has been everything the Padres could have asked for and then some in his two starts this season.
"He's got such a good head on his shoulders," Padres manager Bud Black said. "He knows how to change speeds, mix pitches, knows what he can do to get through the opposition's lineup. He's got great pitching instincts."
Suppan's ERA sits at 0.90, as he has allowed just one run over 10 innings. Filling in for the injured Cory Luebke, he has picked up the win in both of starts, but noted he'd like to be able to work deeper into games and not put as much of a burden on his bullpen.
"I had some command issues, but I just kept battling," Suppan said of his first two starts. "The bullpen did a fantastic job making up some innings there and doing well."
Among active players, Suppan's 413 big-league starts rank fourth in the Majors. (Jamie Moyer's 635 is first, and no one else is close).
As for Hamels (4-1, 2.45 ERA), he allowed just five hits, a run and struck out eight in a badly-needed victory over the Nationals on Sunday. The only run he allowed was Harper coming around to score after he was hit.
Ultimately, Hamels' suspension didn't hurt the Phillies too badly because an off-day allowed manager Charlie Manuel to simply re-shuffle his rotation. That doesn't mean Manuel was OK with missing Hamels, who has been arguably the club's best starter so far.
"He could have been a little bit more discreet about it, or a little less honest," Manuel said.
Padres: Quentin suffers setback
Outfielder Carlos Quentin had a "minor setback" in his recovery from March knee surgery, manager Bud Black said on Saturday.
Quentin is with Class-A Lake Elsinore on a rehabilitation assignment, but didn't play Friday. He then called Black to say that his right knee is still smarting.
"The knee is still a little sore," Black said. "He's still having a little bit of discomfort getting in the box and in his stance with the load on his back leg. We decided to take a step back."
First baseman Yonder Alonso has hit safely in nine straight and in 14 of his last 15 games. In that stretch he is hitting .404, raising his batting average more than .100 points in the process.
Phillies: Fontenot the newest Phil
The Phillies added infielder Mike Fontenot to their roster Saturday after third catcher Erik Kratz was optioned back to Triple-A Lehigh Valley. Fontenot hit .300 with six doubles in 50 at-bats for Lehigh Valley.
Fontenot was a part of the 2010 Giants club that upset the Phillies in the National League Championship Series, but noted he won't bring that up to his new teammates.
"Probably not," he said. "That was fun playing here. I'm part of the Phillies now, but coming in as a Giant I always remember the atmosphere in both parks. It was unbelievable. It was fun to be a part of, but I'm ready to go forward here."
Third baseman Placido Polanco needs just one hit to become the 17th active Major Leaguer with 2,000 hits.
The 224 2/3 innings pitched by Phillies starters is the most in the Majors this year.
A win on Sunday would give the Padres a victory in the season series against Philadelphia, as both teams have earned three victories against each other this season. San Diego hasn't won the season series against Philadelphia since taking four of six in 2006.