Howard hit a two-run homer and Happ threw seven scoreless innings to lead Philadelphia to a 5-1 win over the San Diego Padres on Wednesday night, the Phillies' sixth straight win.
Romero returned from his 50-game suspension for testing positive for a banned substance. The left-hander pitched 1 1/3 innings, allowing an unearned run on two hits, a walk and a passed ball by Chris Coste.
"I was disappointed with my outing, but I'm glad it's over and done with," Romero said.
Romero, who earned two wins in Philadelphia's World Series victory over Tampa Bay last year, retired left-hander Brian Giles opening the ninth, then made way for Ryan Madson. Romero pumped his fist and gazed skyward as he walked to the dugout, where he received handshakes from his teammates.
Romero came on to open the eighth with a 5-0 lead. He allowed David Eckstein's RBI single with one out. After walking Adrian Gonzalez, the major league home run leader with 22, Romero got Kevin Kouzmanoff to line out to shortstop Jimmy Rollins, who doubled Eckstein off second to end the inning.
"I really wanted to put hitters away when I could, but at least I found a groove, when I came out in the second inning, I did what I'm supposed to do, which is getting good left-handed hitters out. But I know with my stuff I should be able to put right-handers away when they're behind in the count."
Howard hit a two-run homer to straightaway center field off Chris Young with two outs in the first, his 16th. Tony Gwynn Jr. turned and ran to the fence, then watched the ball sail over his head. Shane Victorino was aboard on a double down the right-field line.
"I dug us a hole with the Howard ball," Young said. "That's really the one pitch I'd really like to have back. I wanted the pitch down and away and I elevated it. He got extended. If he gets extended, he's so strong that even though he didn't hit it well enough, he's so strong it doesn't matter."
It was Howard's second homer of the series and the sixth for the Phillies. Philadelphia swept this three-game series by scoring 20 runs on 33 hits, including 15 for extra bases.
Happ (4-0) held the Padres to four hits in seven scoreless innings, the longest of his eight career starts over two seasons. He struck out four and walked two.
"I just tried to be aggressive. I mixed it up early in the game a little bit more and kept the off-balance, I guess," Happ said.
"He likes to throw inside and was able to hit the inside corner with it," Eckstein said.
Young (4-4) allowed three runs and five hits in six innings. The Padres lost for the fifth time in six games.
Pedro Feliz hit a sacrifice fly in the fourth and the Phillies added two runs against Greg Burke in the seventh, one of them unearned because of left fielder Will Venable's fielding error. Jayson Werth hit an RBI single and Raul Ibanez drove in a run on a fielder's choice.
Victorino left after the top of the sixth with a strained left hip. He will be reevaluated on Friday before the Phillies open a four-game series at the Los Angeles Dodgers. He was replaced by Werth. ... Still fighting the flu a day after the shortest start of his career, Padres ace Jake Peavy said Wednesday that he should be able to make next scheduled start. He lasted only one inning in a 10-5 loss on Tuesday. ... Padres OF Scott Hairston was placed on the 15-day DL with a strained left biceps. Will Venable was recalled from Triple-A Portland and started in LF.