Tommy Pham’s second tenure with the Mets is finished after only two weeks, and another veteran bat is headed to Queens. Pham was informed Sunday night that he will be designated for assignment. The club has signed Austin Slater, according to industry sources. Slater, 33, owned a .460 OPS in 11 games with the Marlins this season before his release. Pham, 38, was 0-for-13 at the plate in a part-time role after arriving on a minor league deal. As the starting left fielder in Game 1 of Sunday’s doubleheader, he went 0-for-2 and did not appear in the nightcap. The Mets lost 3-1 and 3-0 to the Rockies. Nolan McLean was “pretty happy” with his start Sunday, but it was hardly his cleanest outing of the season. The Mets rookie worked into the sixth inning in Game 1 of Sunday’s doubleheader but never recorded an out before he was removed with the bases loaded in the team’s 3-1 loss to the Rockies. The Rockies also produced traffic in the fourth, driving up McLean’s pitch count.…