ST. LOUIS — The Mets didn’t bother waiting until getaway day to extend their string of series victories.

Tuesday night, behind a strong pitching performance from Chris Bassitt, they beat the Cardinals 3-0 at Busch Stadium to establish a franchise record by winning a sixth straight series to begin the season.

Bassitt followed Max Scherzer’s seven-inning shutout a night earlier by pitching six scoreless innings, in which he allowed two hits and three walks with a hit batsman and struck out six.

The Mets (14-5) will have Carlos Carrasco on the mound Wednesday afternoon against Steven Matz as they pursue their first series sweep of the season.

Bassitt struggled against the Giants in his last start, surrendering five runs over six innings in a loss, but he avoided trouble on this night after the first inning, when the Cardinals had two runners on base.

Right-handed batters went 2-for-13 with five strikeouts against Bassitt, who entered the night having allowed only one hit in 26 at-bats to righties.

Pete Alonso got drilled in the helmet by a Kodi Whitley changeup in the eighth inning. Alonso mouthed a few words to the pitcher after arising and trotting to first base and Mets players briefly trickled from the dugout, stopping before they reached the field. Alonso was examined at first base by the trainer, but remained in the game.

It was a second scary incident for Alonso, who got drilled in the jaw flap extension during the opening series in Washington.

In the ninth inning, Starling Marte got plunked by Aaron Brooks with the bases loaded to bring in the Mets’ final run. The Mets have been hit by 17 pitches this season, which leads the major leagues.

Adam Ottavino drilled Tommy Edman near the ankle leading off the bottom of the eighth. In the sixth, Bassitt hit Nolan Arenado in the midsection.

Drew Smith, Ottavino and Edwin Diaz each pitched a shutout inning in relief. Smith continued to impress, extending his scoreless streak to six appearances to begin the season.

The Mets jumped on Jordan Hicks for two runs in the third to take a 2-0 lead. Jeff McNeil and James McCann stroked consecutive doubles for the first run, and Marte’s scalding RBI single past third base added another. Hicks departed with a right wrist contusion before the inning was complete.

McCann’s double to the center-field fence was his second loud hit on the road trip. The slumping catcher also mashed a home run Friday night at Arizona that was significant in the Mets victory.

Edman walked in the third and stole second against Bassitt and McCann before the right-hander struck out Paul Goldschmidt and Tyler O’Neill to end the threat.