SAN FRANCISCO -- As general manager Sandy Alderson stood in the visitors' dugout at AT&T Park during batting practice on Thursday afternoon, a New York Mets fan in the crowd shouted at him, "Bud Black! Bud Black, Sandy! Bud Black!"

Alderson turned his back and tried to conceal any visible reaction to the heckler, who was imploring the GM to hire Black, a free-agent manager.

Alderson then told ESPN.com he is not currently contemplating any changes with Mets manager Terry Collins or his staff.

Manager Terry Collins and the New York Mets have gone 13-19 since the All-Star break, dropping them four games behind the St. Louis Cardinals for the second NL wild-card spot entering Thursday's games. Jim McIsaac/Getty Images

Alderson would not offer a blanket guarantee they would survive the season, though.

"Do I ever make any statement unequivocally?" Alderson said. "There are no present plans to make any changes."

After winning the National League pennant in 2015, the injury-depleted Mets are 60-60 this season as they open a four-game series against the San Francisco Giants. The Mets are only 13-19 since the All-Star break, which has dropped them four games behind the St. Louis Cardinals for the second wild-card spot.

The Mets are getting some reinforcements soon. Justin Ruggiano (hamstring) was activated from the disabled list on Thursday, and Yoenis Cespedes (quadriceps) and Asdrubal Cabrera (knee) are set to be activated Friday.

Still, Neil Walker remains sidelined for a third straight game with a back injury. And the Mets have lost David Wright, Lucas Duda, Matt Harvey and potentially Juan Lagares for the season.

Asked if observers, including the AT&T Park heckler, are being too harsh -- given the volume of the team's injuries -- Alderson replied: "We all have an expectation of winning. None of us uses injuries as an excuse. That's true inside the organization. That's true for our fans, as well. That's why I understand the frustration."