Mets Fall to Marlins in 20 innings Andy Marlin/Getty Images The Mets' Matt Harvey left the game before the start of the eighth inning after experiencing muscle tightness in his lower back. Matt Harvey, his head lowered, received a standing ovation from the small Citi Field crowd as he walked off the mound and toward the Mets" dugout late Saturday afternoon. It was a familiar show of appreciation toward the young ace, but this time it came under worrying circumstances. All afternoon, Harvey had been polishing another gem, having allowed only one run to the Miami Marlins, and he was warming up to pitch before the start of the eighth inning. But something was not right. Soon, Manager Terry Collins and a team trainer were jogging to the mound, and after a short conference, Harvey was handing over the ball and leaving the field. He appeared to gesture toward his back before ducking into the home clubhouse, and the Mets announced a few minutes later that Harvey had experienced muscle tightness in his lower back. Several hours later, the Mets lost the game, 2-1, after 20 innings lasting 6 hours 25 minutes. It was the longest game played at Citi Field. As the innings wore on, the game grew gradually more absurd, as baseball's two worst-hitting teams seemed incapable of summoning one more run. And still, such things as wins and losses felt insignificant on a day when the health of the team's best performer this season appeared to be jeopardized. Any layoff for Harvey will be demoralizing for him, the team and Mets fans. Harvey, a 24-year-old right-hander, has represented one of the few positive glimmers during this disheartening Mets season. He pitched seven innings Saturday, allowing six hits and no walks while striking out six batters, and he lowered his earned run average to 2.10. The ballpark crowd was officially listed at 20,338, but it seemed as quiet as a Zen garden as Harvey was being checked on the mound. Harvey had singled the previous inning, and it seemed possible he injured himself running the bases. The fans who remained after that watched the teams take turns stranding runners on base. The ineptitude was at first startling, then maddening. The Mets put a runner into scoring position eight of their last 12 innings, but failed to push across the winning run. They went 0 for 19 with runners in scoring position, a franchise record. Relief swept through the ballpark long after the last slivers of sun disappeared from the field. Adeiny Hechavarria smacked a run-scoring single to left off Shaun Marcum in the top of the 20th inning, stirring a halfhearted mixture of boos and applause from the crowd. Marcum, the eighth pitcher the Mets used, was charged with the loss. He pitched eight innings, allowing just five hits and the one, decisive run. Kevin Slowey, the Marlins" seventh pitcher, dueled him, tossing seven scoreless innings. Steve Cishek closed the 20th inning for the save. The Marlins arrived to Citi Field having won three times over their last 15 games. All three victories came against the Mets last weekend, and the Marlins proved a pesky rival once again. Of their 17 victories this season, 7 have come against the Mets. The first of the game's two pitchers" duels pitted Harvey against Jose Fernandez, the Marlins" 20-year-old right-hander. Harvey, trying to bounce back from a subpar outing against the Marlins last Sunday, was hot from the start, firing 98 miles-per-hour fastballs as he retired 10 of the first 11 batters he faced. During the sixth, he hit 99 m.p.h. three times. Fernandez, a bright orange glove flapping on his left hand, could not match Harvey's early tidiness, though he nevertheless secured a similar outing. He lasted six innings and allowed just one run. He wriggled from a first-and-third jam during the first inning, but encountered more trouble to begin the second. Ike Davis, batting sixth for the Mets, drew a walk to start the inning. One out later, Davis was galloping home from first base on Juan Lagares's double to left field, his helmet fluttering off his head somewhere near third. Lagares, a young reserve finally getting an extended center-field trial, contributed on defense, too. In the fifth inning, with the score tied, Hechavarria tried to score from second on Juan Pierre's soft single to center, but Lagares charged the ball and fired a one-hopper home to nab him there. Before Harvey's injury, his lone slipup came during the fourth. He gave up consecutive one-out singles, then let Chris Coghlan float a ball to right field for a sacrifice fly that tied the score at 1-1. Sixteen innings later, the Marlins got their second run. The Mets on Saturday morning promoted the right-handed relief pitcher David Aardsma from Class AAA, optioning the right-hander Collin McHugh to the minors. Aardsma, 31, who had Tommy John surgery in July 2011, last pitched in the major leagues in 2012, when he made one appearance for the Yankees. The club moved Jeurys Familia (elbow) to the 60-day disabled list to make room for Aardsma on the 40-man roster.