Acquired in a four-player trade from the Los Angeles Dodgers for Hanley Ramirez earlier this week, the 22-year-old right-hander allowed one run and five hits in 5 1/3 innings in a 4-2 victory over the San Diego Padres on Saturday night.
"It was great," Eovaldi said. "I worked ahead a lot. Me and (catcher John) Buck got on the same page early on in the game and there were great plays made behind me."
Eovaldi (2-6) struck out five and walked two.
"One of the things that stood out to me right away when as we went over our game plan, the only other person that young that I've had that had an idea what he wanted to do was probably Zack Greinke," Buck said. "He was able to go out and execute it. For a young guy that's a big step."
"We did today what we've been missing for a long time, get big hits," Marlins manager Ozzie Guillen said.
Yonder Alonso had two doubles and drove in a run for the Padres, who had won seven of 10.
The Marlins had scored three runs or fewer in nine consecutive games, which matched a franchise record set in 1994.
Carlos Lee's RBI single in the first gave the Marlins an early lead.
Eovaldi reached base on an infield single in the third and scored on Reyes' shot to right field off Ross Ohlendorf (3-1) for a 3-0 advantage. The home run extended Reyes' hitting streak to 15 games, tying a season high.
"Every time Jose is on the baseball field he can make a lot of great things happen," Guillen said. "Jose has been doing great, he's not hitting .390, but he's playing better than what people think. He hits the ball very hard, more than what people think. Reyes is a guy we are going to play around."
The Padres strung together three hits in the sixth, including Alonso's run-scoring double, to end Eovaldi's night.
"(Eovaldi) has a great arm," Guillen said. "You can see he's still a baby, can still be polished, but I love his arm and his presence on the mound is very good."
"We had some opportunities, but we didn't cash in," Padres manager Bud Black said.
Ohlendorf allowed three runs in six innings.
"Aside from the third inning, I thought I was throwing really well," Ohlendorf said.
Marlins All-Star slugger Giancarlo Stanton, who has not played since July 7 because of right knee surgery, is aiming for an Aug. 10 return. "It's not fun to just sit there helpless," Stanton said. "You still pick up some things, learn from the down times we are going through, that's all you can do. I'm eager to get back. I'll be ready." ... Marlins LF Logan Morrison was dropped to seventh in the lineup after an 0-for-14 slump. "If he keeps swinging like that, he'll be my bench coach," Guillen said. "That's easy. I've got to go back to being Ozzie." ... Alonso recorded his eighth game with two-or-more doubles, which is a Padres record and the most by any player in the Majors this season. ... The Padres had won nine consecutive games over the Marlins in South Florida. ... Marlins RHP Josh Johnson (6-7, 4.14 ERA) will oppose Padres LHP Clayton Richard (7-11, 4.17) in Sunday's series finale.