Cincinnati trailed 4-2 before Castellanos connected for his sixth career grand slam, driving a 1-1 fastball from Neftali Feliz (0-1) deep to center for his 15th homer. Castellanos thrust his fist in the air as he circled the bases.
It was Feliz’s first big league appearance since 2017. He came on after Bailey Falter pitched four innings of one-run ball in relief of Spencer Howard.
Cincinnati’s seventh-inning rally was sparked by Alejo Lopez, who was called up earlier in the day from Triple-A Louisville. He pinch-hit with one out and singled on the first pitch.
The Reds added six more in the eighth, blowing it open against the Phillies’ sputtering bullpen. Eugenio Suárez and Tyler Stephenson scored on a throwing error by reliever Enyel De Los Santos. Castellanos drove in Jonathan India with a two-out double, and Joey Votto added a solo drive.
Alec Bohm and Ronald Torreyes each drove in two runs for the Phillies.
Heath Hembree (2-3) pitched a scoreless inning for the win.
Phillies: RF Bryce Harper was back in the lineup after sitting out Sunday’s game with some tightness and swelling in his left calf. He left Saturday’s game in the sixth after he was hit by a pitch on that leg. … 2B Jean Segura (groin strain) and SS Didi Gregorius (right elbow) are close to be activated, according to manager Joe Girardi.
Reds: CF Tyler Naquin was scratched because of a sore right wrist. Shogo Akiyama started in his place. … RHP Sonny Gray (groin) said he will start for the Reds on Friday after a rehab outing at Triple-A Louisville. … Manager David Bell said RHP Jeff Hoffman (shoulder) will make another rehab start at Louisville before rejoining the team.
Phillies: Head home Tuesday for a three-game series with Miami. Left-hander Trevor Rogers (7-4) is expected to start for the Marlins against right-hander Vince Velasquez (2-2).
Reds: Send right-hander Tony Santillan (1-1) to the mound to face left-hander Blake Snell (3-3) for the first of a three-game series with the Padres.