ALLENTOWN, Pa. -- With two big swings, Bryce Harper looked primed to join the Phillies in a pennant race.

Harper homered to right-center field in his first at-bat, then went opposite field for a three-run shot in the eighth inning for Philadelphia's Triple-A team Tuesday night to begin his rehabilitation assignment from a broken left thumb.

Harper was the designated hitter and hit second in the lineup for the Lehigh Valley IronPigs for the start of a six-game series against Gwinnett. He drilled the fifth pitch he saw from Atlanta Braves prospect Jared Shuster high over the wall at Coca-Cola Park in front of what was announced as a sellout crowd of 10,100 fans.

"I think any time you go out there and you're able to put the bat on the ball and have good at-bats, see pitches, compete at a high level, it's always good," Harper said.

He walked against Shuster in his second at-bat to the boos of the crowd that wanted Harper to take another hefty hack. Harper was then caught stealing. He grounded out in his third plate appearance, and walked again and scored in the seventh to lead Lehigh Valley past Gwinnett 10-5.

Gwinnett had some fun after Harper's solo homer cut the Stripers' lead, tweeting "Phillies prospect Bryce Harper goes deep to cut the Stripers lead 3-1. Admittedly, he looks like one to watch in the future."

And before Harper's fifth time up, the scoreboard read: "Today 1-2 Bryce Bomb." Make it two.

Harper, who won his second NL MVP award last year, hasn't played for the Phillies since he broke his left thumb on June 25. He is expected to play in Lehigh Valley through Saturday and possibly return to the Philadelphia lineup on Monday when the playoff-contending Phillies begin a series at Arizona.

But with two homers in his first rehab game, why wait until Monday to add him to a team that very much needs him now?

"Tonight was great, right? But at the same time, I need the at-bats, I need to be able to see pitches, different guys, different angles, understanding how my body's going to react, what my thumb's going to be like," Harper said.

The 29-year-old Harper, who signed a $330 million, 13-year deal with the Phillies in 2019, is hitting .318 with 15 home runs, 48 RBIs and a .985 OPS. Harper had already surrendered his spot in right field earlier this season because of because of a small tear in the ulnar collateral ligament of his throwing elbow. He last played the field at Miami on April 16.

Asked if he could play right field in September, Harper simply said, "no."

The Phillies outlasted the Cincinnati Reds 7-6 on Tuesday night and remained in the thick of the NL wild-card race. After the win, Phillies interim manager Rob Thomson said the staff will talk to Harper about his return date, and did not rule out Friday as a possibility.

"Bring him up. He doesn't need more games," Philadelphia second baseman Jean Segura said after the win. "What is he doing down there? He's ready. Hopefully he comes back quick. If he hit two homers, bring him up."

Harper was a smashing success for the fans that turned out in season-high numbers to catch a glimpse of one of baseball's most popular players.

The IronPigs merchandise store and ticket phone lines were buzzing each of the last two days in anticipation of his arrival. Will he play? Will jerseys be on sale? What time do gates open? One cashier looked out the team store window and noted, "I've never seen at 5:12, just hundreds of people standing out there."

Mike Luciano, director of merchandise, faced an early jam when Harper decided to change his uniform number for his minor league stint. While an attraction, Harper did not want to serve as a distraction for the IronPigs and allowed reliever Jonathan Hennigan to keep his No. 3 while the slugger bumped up one to No. 4.

"I ordered a lot of 3s," Luciano said. "Luckily, the 4s came in."

Harper T-shirts were truly hot off the press. About 90 minutes before first pitch, roughly 150 Harper shirts were still as warm as a ballpark hot dog as they quickly shuffled from print to merchandise store racks. The blue No. 4 shirts sold for $28 and a limited number of customized jerseys went for $110. Sales sizzled at a better rate than the usual top sellers, which would be, Luciano said, "anything with bacon."

"You put a bacon strip on a hat, people love it," Luciano said.

Chris Philpott, of Allentown, bought two game tickets in the morning and snagged a Harper T-shirt in the store. He usually attends about 12 IronPigs games a year and just had to get seats for Tuesday night.

"I got here early because my kid was hoping to catch him on BP," he said. "We saw all the cameras when we came in. It's going to be nuts tonight. You don't normally see people lined up when there's no giveaway this early before the game opens."

Harper skipped hitting on the field, but that didn't keep fans from hanging over the railing near the IronPigs dugouts in hope of catching a peek at the two-time NL MVP. TV stations aired live remotes and the press box was full with media outlets normally reserved for covering the Phillies, playing at home down the turnpike in Citizens Bank Park.

Two hours before gates opened, only 80 tickets remained, most down the right-field line. The stadium -- home in the past to similar warm-up stints for Pedro Martinez and Chase Utley -- was full on a night that went to the dogs. Yes, in a nod to a night dedicated to area efforts at dog adoption, Harper skipped the bacon-themed gear for an IronMutts jersey.

Oh, and 195 dogs wagged their tails at the ballpark -- 44 were adopted, and a few mutts can probably thank Harper's cameo for their new homes.

The Associated Press contributed to this report.