Mets fans boo New York mayor as he throws opening day first pitch (VIDEO)

New York Mayor Bill de Blasio was booed at Citi Field on Monday, even before he had a chance to throw out the first pitch.

The lanky, 6-foot-5 right-hander was greeted by Bronx cheers as soon as his name was announced during the Mets opening-day festivities in Flushing.

De Blasio — a noted Boston Red Sox fan, wore a Mets cap and jersey with a No. 6 on it in honor of 1960s-era Red Sox player Rico Petrocelli — tossed a strike to Mets catcher Travis d’Arnaud, and flashed a relieved grin after his pitch reached the plate.

The rookie mayor — in office for only 90 days — played off the boos, suggesting that his supporters might have been too cold to cheer.

Yeah right.

But it was the Mets' bullpen that deserved the jeers after blowing an eighth inning lead before losing to Washington Nationals 9-7.