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In the sixth inning of the first game of the Subway Series, and with the Yankee Stadium crowd beginning to wonder whether Hiroki Kuroda could make a second consecutive New York Friday memorable, Omar Quintanilla knocked a 93-mile-per-hour sinker to left field. Quintanilla’s double was notable for being the Mets’ first hit all evening.

Yet the hit also continued an unlikely string of production for an unlikely starting shortstop. In 10 games this season before a start Saturday against the Yankees, Quintanilla was batting .321 with a .457 on-base percentage. Four of his nine hits had been doubles, which is as many as he hit in all but one of the previous six seasons in which the 30-year-old Quintanilla has logged major league service time.

“There’s been times where I’ve played a certain amount of time and I’ve been able to hit the ball,” Quintanilla said. “But when it comes to pinch-hitting and all that, it gets a little tough for me.”

Entering Saturday’s game, Quintanilla had started 10 games since his May 29 promotion from Class AAA Buffalo. It took an infielder-laden disabled list to earn his opportunity, although there was actually a design to Quintanilla’s even becoming an option for Manager Terry Collins to write in the batting order.

Quintanilla spent 2011 with the Texas Rangers, whose deep middle infield left few opportunities. At the beginning of the off-season, Quintanilla discussed the depth charts of different franchises throughout baseball with his agent. The Mets watched Jose Reyes sign with Miami on Dec. 7 and were turning over the position to Ruben Tejada. On Jan. 3, Quintanilla signed a minor league deal with the Mets to provide depth at a position that had few established options.

And, in two months, the Mets have exhausted that depth. Quintanilla is the team’s sixth shortstop of the season after Tejada, Ronny Cedeno, Jordany Valdespin, Justin Turner and David Wright (an emergency fill-in). Tejada, Cedeno and Turner are on the disabled list, Valdespin remains raw defensively and Wright, of course, is the starting third baseman.

Reyes, a four-time All-Star and the 2011 National League batting champion, has started all but one game for the Marlins. At this point, Collins will be pleased if Quintanilla even brings a bat to the ballpark.

“At his spot, if he hits, that’s a plus,” Collins said. “I want him to catch the baseball behind that pitching staff and make the routine play.”

In Collins’s repeated conversations with Wally Backman, the manager of the Mets’ Class AAA team in Buffalo, Backman told Collins, “If you need a defensive shortstop, we got one.” Collins referred to a recent victory over the Washington Nationals in which Quintanilla’s glove was pivotal for the victory.

“I’m not sure if a guy like himself is not at shortstop that we don’t win that game,” Collins said. “That’s what we need out of him, to make those plays.”

Quintanilla — and the Mets, for that matter — had a brief worry when he sustained a small fracture in his left index finger last week. Collins waited until the final hour to submit a lineup for Thursday’s game against the Nationals because of concern about whether Quintanilla could play. Quintanilla was concerned, too.

An absence of any duration could complicate his standing on the roster. If he had a more secure job or the Mets had more options, such an injury might garner at least one day off. Quintanilla is enduring a stinging sensation when he catches the ball because the alternative is someone else playing in his spot.

“When you get an opportunity like this and you get an injury, you want to keep playing,” Quintanilla said. “For me, I’ve been playing through this the past couple days, and I can handle this.”

In 2010, Major League Baseball suspended Quintanilla 50 games for testing positive for a performance-enhancing substance. It was the low point of his career, and he continues to maintain his innocence, saying he took a supplement from G.N.C. that he did not know anything about. Since then, he has been trying to find a consistent spot in the majors. Now that he has a temporary one, he is determined to maximize the opportunity.

Quintanilla does not know how long it will long it will last — Cedeno and Turner could soon return, and Tejada will most likely return in a few weeks — but playing every day at least provides a chance that has eluded him through much of his career.

“It is about trying to prove and open eyes and show people you can help a team win,” Quintanilla said. “It’s in the back of your mind that you could be demoted and go back down. So you try to clear all that away and go play ball.”