Whether the series begins in Chavez Ravine or in this corner of Flushing, little doubt exists about Jacob deGrom's standing in the starting rotation.

Once the Mets qualify for the postseason -- a virtual technicality with the way they've exploded past the Nationals -- the 2014 NL Rookie of the Year almost certainly will get the ball within the first two games of the NLDS.

Which is why the only reason for pause to emerge from Tuesday night's 9-3 loss to the Marlins stemmed from the pitcher's mound. Aside from his signature locks, deGrom looked little like himself, retreating after five innings of surrendering loud contact on fastballs that caught far too much plate.

For the first time since Sept. 6, also against the Marlins, the Mets lost. Their eight-game winning streak became just another footnote in a magical season.

Though the Mets did not reduce their magic number of 10, the Nationals remain but a speck in the rearview mirror, trailing by 81/2 games in the NL East.

But deGrom's struggles carry far more weight than the defeat's impact on the standings.

For the first time this season, deGrom allowed double-digit hits (10), most of them liners. The only other time he allowed that many hits was when he gave up 12 to the Cardinals in his brilliant rookie season.

Against the Marlins, the wheels came off in the fourth, when he allowed four hits for a 3-1 deficit.

The fifth brought more gloom, three more runs and four hits, including doubles to his Marlins counterpart Tom Koehler and Christian Yelich.

DeGrom had his worst start since pitching through illness Aug. 24, when the Phillies roughed him up for eight runs in just 22/3 innings.

In his last five outings, which includes a gem against the Nationals, deGrom (13-8) has a 6.41 ERA. His ERA for the season rose to 2.64, its highest point since May.

Though deGrom entered the season without a strict innings limit, his recent downturn has prompted the Mets to examine pushing back his next start to give him extra rest.

Noah Syndergaard's brilliance Saturday -- which came after his previous turn was skipped in the rotation -- only emboldened manager Terry Collins to push for the same with deGrom.

Perhaps the Mets had the Marlins right where they wanted when deGrom left the game trailing 6-1. According to the Elias Sports Bureau, each of the last five times the Mets trailed in the sixth inning or later, they rallied to win. It had been the longest such streak in team history.

But this time, there would be no comeback.

The Mets missed their chance to force the Marlins to climb out of a hole. In the first, David Wright had an RBI double. But Travis d'Arnaud and Lucas Duda followed with pop-ups. So it went for the Mets, who squandered potential rallies in the fourth, sixth and seventh against Stony Brook product Koehler, who raised eyebrows earlier.

Koehler plunked Yoenis Cespedes in the side, drawing a cold stare from the Mets slugger on his jog to first base. Nothing came of it.

But later, as Koehler squared to bunt in the seventh, he watched an Erik Goeddel fastball sail behind his back. Koehler (10-13) struck out, though he ultimately emerged with the victory, holding the Mets to only one run in six innings.