LOS ANGELES – Kodai Senga had a disappointing start in which there was little mystery about what went wrong: He couldn't find the sign.

David Peterson came in later and delivered a similarly disappointing performance that bore little other resemblance.

Peterson found the plate, but also the Dodgers' barrels, which were hit hard for the first time this postseason.

The Mets' Plan A failed before the Mets' Plan B failed to result in a 9-0 loss in NLCS Game 1 at Dodger Stadium on Sunday night.

Peterson, one of the Mets' most valuable players early in the postseason with 6 ¹/₃ scoreless innings in relief in October, looked far more lethal against the Dodgers than he did against the Brewers and Phillies.

Arguably the Mets' best bullpen arm allowed three runs (two earned) on four hits and a walk over 2¹/₃ innings against perhaps the best lineup in baseball.

All of the damage against Peterson came in the fourth inning, where the Dodgers converted four singles, a sacrifice and an error by Starling Marte into a three-run frame that tied the game.

In the inning, Kiké Hernandez singled to right and advanced to second base after a bunt by Gavin Lux.

Tommy Edman's single made it 4-0 before Peterson gave up an inadvisable curveball to Shohei Ohtani over the middle of the plate.

Ohtani blasted the ball off the bat and off the wall in right-center at 116.5 miles per hour.

Marte dropped the carom off the wall, which was important as Edman slid in safely just before the relay throw.

With Mookie Betts down – even the out was beaten off his bat at 101.6 mph – Freddie Freeman sent a single into left field, and Brandon Nimmo's throw home was too late to catch a slipping Ohtani.

From there, Peterson calmed down, but only threw a pitch until the fifth inning in a 40-pitch outing, meaning he won't be available for Monday's game and likely won't be sufficiently stretched for a longer start in either Game 5 if the Mets decide to move on from Senga.

After a late start to the season following offseason hip surgery, Peterson was reliable and excellent for the Mets during the regular season, posting a 2.90 ERA in 21 starts.

A valued lefty for a team without many lefties in the bullpen and with bullpen experience, he was taken out of the rotation in October for Sean Manaea, Luis Severino, Jose Quintana and a stretching Senga.

Immediately after Sunday's defeat, the question arose as to whether Peterson would be relegated or Senga would jump into the starting group.