MIAMI — Now even the tradable pieces are starting to stink up the joint for the Mets.

After Zack Wheeler sent the Mets into the All-Star break with a clunker, on Friday it was Jason Vargas who perhaps detracted from his own trade value, getting clobbered by the Marlins, who have the lowest-scoring lineup in the National League.

In his worst start this season, the veteran left-hander allowed six runs over five innings, sending the Mets to an 8-4 loss to begin the second half. The Mets fell 11 games below .500 for the first time this season and dropped to 17-32 on the road.

“It’s not fun to lose the first game back, but it is one game,” manager Mickey Callaway said.

Vargas was the Mets’ second-best starting pitcher, behind only Jacob deGrom, in the first half. But Friday he allowed two homers in the third inning and then got knocked out in the sixth, before Robert Gsellman entered and surrendered a two-run homer to Brian Anderson.

“I definitely wasn’t as sharp as I had been,” Vargas said. “But I had some pretty solid innings.”

The Mets hold a club option on the 36-year-old Vargas for next season, but could deal him before the July 31 trade deadline in an attempt to get something of value for a pitcher who may not fit their plans. Wheeler, an impending free agent, is the most likely Met to get traded. Todd Frazier, who homered in the ninth, is another possibility to be dealt.

Vargas’ night began to unravel in the third inning, when he allowed consecutive homers to Curtis Granderson and Garrett Cooper that gave the Marlins a 4-2 lead. Vargas’ preoccupation with the pitcher Caleb Smith, who was on first base, might have contributed to Granderson’s blast. After throwing to first base six times — including three straight — Vargas hung a change-up that Granderson swatted for his eighth homer of the season. Cooper unloaded next.

But Vargas defended his decision to keep throwing to first base with Smith aboard.

“You usually don’t see the pitcher dive back, especially more than once,” Vargas said. “And it takes a lot out of you to do it. “It didn’t work out, but I don’t know if that was the reason for the bad pitch [to Granderson].”

Jorge Alfaro singled and stole second to begin the inning. After Smith singled, Miguel Rojas’ sacrifice fly gave the Marlins their first run.

Wilson Ramos’ two-run single in the third built a 2-0 lead for the Mets. Smith could have escaped the inning without a run, but Cooper’s throwing error allowed Jeff McNeil to reach second base after he had been picked off first. J.D. Davis and Pete Alonso followed with walks that loaded the bases before Ramos delivered the two-out hit.