The Mets brought in Edwin Diaz for a scoreless seventh inning, a hopeful sign that the typical shutdown closer is OK.
But whatever has been wrong with Diaz might have been infectious.
It is the usually excellent Reed Garrett who has come down with something and let up five eighth-inning runs — the largest swing a grand slam from Giants catcher Patrick Bailey — that shifted the result of a stunning 8-7 Mets loss Friday night to open a series and homestand at Citi Field.
Even after Garrett’s rough frame, the Mets mounted a ninth-inning rally and loaded the bases with one out.
All those base runners were stranded.
The Mets (21-29) lost a fourth straight, a sixth in their past seven and a ninth in their past 11.
They are free-falling, and this one ranks among the most painful in the nosedive.
They entered the eighth inning cruising, up four runs and able to turn the game over to Garrett and Adam Ottavino.
But Ottavino never entered because of the disastrous eighth.
If it is any consolation, much of the contact was not particularly hard.
Garrett got into trouble because Mike Yastrzemski reached on a swinging bunt that hit the third-base bag, and Marco Luciano blooped a single.
With two out, former Yankee Thairo Estrada doubled in one run before Garrett lost Matt Chapman on a seven-pitch walk that loaded the bases.
Garrett’s 25th pitch of the outing was a four-seamer that got too much of the plate, with Bailey rocketing it to right-center for a grand slam.
Once the inning was over, Garrett — perhaps the best find of this season — was booed all the way to the dugout by the 26,658 on hand.
The Giants added another run in the ninth on a Yastrzemski homer off Jorge Lopez, a run that would matter.
In the bottom of the inning, the Mets scored once on an RBI double from Francisco Lindor.
They then loaded the bases with one out, but fireballing closer Camilo Doval struck out J.D. Martinez on three pitches.
Mark Vientos hit a slow roller down the third-base line.
Gold glover Matt Chapman bare-handed and threw to first just in time to lock up one of the crueler ways to lose a game.
Garrett’s pitching erased both a lead and so much goodwill that the Mets had built for the previous seven innings.
Wasted was six strong, two-run innings from Christian Scott, who likely believed he would notch the first win of his career in his fourth start.
Wasted were three more home runs — the third-straight game the Mets have launched a trio of homers, and the third straight game those blasts have not mattered — including back-to-back shots from Martinez and Vientos, plus the 12th of Pete Alonso’s season.
Wasted was more hope from Vientos, who is hitting .344 in 10 games and continuing to try to win a full-time job.
The Mets have stuck with Brett Baty, who could get looks the next two days against righty Giants starters but whose time might be running out.
Wasted was a solid seventh inning from the previously struggling Diaz, who had not pitched since Saturday and entered in a lower-leverage spot.
At last, Diaz looked like Diaz, only allowing a single in a scoreless inning while striking out two.
