For a second straight night, the Arizona Diamondbacks rallied late to stun the Philadelphia Phillies in the National League Championship Series.

Arizona scored three times in the eighth inning, highlighted by Alek Thomas' pinch-hit, game-tying two-run homer, to earn a critical 6-5 win over the defending NL champions in Friday's Game 4 that evened the best-of-seven series at two games apiece.

After losing Games 1 and 2 in Philadelphia by a combined score of 15-3, the Diamondbacks got back into the series with Thursday's 2-1 comeback victory in Game 3, in which they trailed 1-0 in the seventh inning and won it on Ketel Marte's run-scoring single off Phillies closer Craig Kimbrel in the ninth.

Kimbrel came on in the eighth of Game 4 to protect a 5-3 Phillies' lead and again faltered. Lourdes Gurriel Jr. led off Arizona's half of the inning with a double and two batters later, Thomas drove a pitch into Chase Field's swimming pool in right-centre field to tie the contest.

Marte later singled with two out and Kimbrel hit Corbin Carroll with a pitch to set the stage for Gabriel Moreno, who greeted reliever Jose Alvarado with a single to center that drove in Marte for a 6-5 Arizona edge.

Philadelphia got the tying run in scoring position in the ninth when Kyle Schwarber doubled with two out, but Diamondbacks closer Paul Sewald struck out Trea Turner to end the game and keep the momentum in Arizona's favour.

In a series where the home team has won every time thus far, the Diamondbacks will host Game 5 on Saturday.

Arizona took a 2-0 lead on Emmanuel Rivera's RBI single in the second inning and Moreno's base hit in the third that also plated Marte, but the battle-tested Phillies responded with five runs over the next four innings to forge ahead.

Schwarber got them on the board in the fourth with his fourth home run of the series and Brandon Marsh doubled home J.T. Realmuto in the fifth to create a 2-2 tie. The Phillies then took advantage of wildness and a defensive miscue by the young Diamondbacks to score twice more in the sixth.

Andrew Saalfrank, one of eight Arizona pitchers used on the night, walked Schwarber, Turner and Bryce Harper in succession to load the bases for Alec Bohm, who delivered an infield single to send home Schwarber with the go-ahead run. Third baseman Rivera threw errantly to home plate on the play, allowing Turner to score as well and put Philadelphia ahead 4-2.

The Phillies tacked on another run when Johan Rojas tripled in the seventh and scored on Turner's sacrifice fly.

Both Schwarber and Bohm had two hits and an RBI for the Phillies. Moreno finished 2 for 3 with two RBIs for Arizona, while Marte had two hits and scored twice.