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9/1/2013 12:50 A.M. ET

Ike's season could be over with strained oblique

WASHINGTON -- A trying season likely came to an end for Mets first baseman Ike Davis on Saturday night, when he sustained a strained right oblique while taking a swing in the third inning and had to leave the Mets' 11-3 win over the Nationals.

"If it's an oblique and if it's serious, it'll be difficult for him to come back before the end of the season," Mets general manager Sandy Alderson said.

Davis, who will return to New York to be examined further, will not go on the disabled list with rosters expanding on Sunday. But with a month left in the season, it's unlikely he would have time to recover, rehab and return to the Mets.

"What we've seen from Justin [Turner] and [Lucas] Duda and anybody else who's had it, not only this year, it's three weeks before you're even back doing baseball stuff, and that's only one week left, so I doubt we see him," Mets manager Terry Collins said.

"I feel terrible for Ike. He went to the Minor Leagues, worked very hard on some things, came back, started to see some signs ... 2013 is going to go down as a real frustrating year for Ike Davis."

Davis was hitting .161 with a .500 OPS when the Mets demoted him to Triple-A Las Vegas in early June. When he returned about a month later, his performance spiked. After going 0-for-1 with a sacrifice fly on Saturday, Davis was left with a .453 on-base percentage since the All-Star break and a .473 mark in August, with 24 walks. He also had hit three home runs in his past 13 games to give him nine for the year.

"I kind of found where I needed to be in my stance and my rhythm and where my hands should be, so I was actually really excited with how I swung the bat the last couple weeks, starting to hit the ball in the air consistently, which leads to home runs," Davis said. "Obviously, I can play better than I did in the first half, because I showed that I can. Hopefully, I can do it for two half seasons next year."

If Davis' season is over, he'll finish with a .205/.326/.334 line and 33 RBIs in 377 plate appearances. He admitted that all the work he did trying to correct his problems at the plate might have led to the injury.

"Obviously, I did swing a ridiculous amount for a long time trying to figure out how to play again," he said.

Davis had felt some tightness in his side for a couple of months, and during that time, he believed a strain could happen anytime. But the discomfort had gone away about a week ago, so Davis was surprised when he hit a sac fly to left field in the third inning and grabbed his side in pain.

After the game, Davis said he felt OK standing up. But earlier he was eating sunflower seeds on the bench, and when he coughed, "it felt like someone stabbed me."

"I don't think that's a good sign," he said.

With Davis out, Collins said that Lucas Duda, recently recalled from Las Vegas, will take over primary first-base duties. Josh Satin also will get some time against left-handed pitching. Alderson added that the club likely will call up a player from Las Vegas to add to the roster.

Mets put den Dekker in center, Lagares in right

WASHINGTON -- The Mets' Matt den Dekker made his second Major League start on Saturday night against the Nationals, and this time, manager Terry Collins put him in the same outfield as Juan Lagares. Collins wanted to see den Dekker in center and Lagares in right, an alignment that gives the Mets speed across their outfield, with Eric Young Jr. in left.

"And we've got to look down the road, too," Collins said. "You've got to find out what Matt den Dekker can do. Is he gonna to be able to handle this level?"

den Dekker delivered his first Major League hit and RBI with a single to left field during a six-run third inning in the Mets' 11-3 win over the Nationals, while Lagares contributed his National League-leading 12th outfield assist by gunning down Bryce Harper at third base.

The Mets brought up den Dekker when they traded Marlon Byrd to the Pirates, and the 26-year-old debuted in center on Thursday, with Andrew Brown in right. He went 0-for-5 but stole a base and scored a run.

Collins liked the left-handed den Dekker's matchup against Nationals righty Dan Haren on Saturday, because the veteran doesn't have an overpowering arm. With den Dekker and Lagares starting, Brown was on the bench, despite his recent hot streak.

"I just want to get Matt in there enough so we have at least an idea of what direction we need to go in next year," Collins said.

Lagares, also a rookie, had made all 70 of his starts in center before Saturday and had played all of three innings in right. But he also spent considerable time at all three outfield spots in the Minors, and he will continue to play center when den Dekker isn't in the lineup.

"You just explain the situation," Collins said of moving Lagares.

"Matt's played two games in the corners, so I just don't think it's fair for Matt to play anyplace but where he's most comfortable when he's in the lineup."

d'Arnaud settling in after back-to-back multihit games

WASHINGTON -- Mets catcher Travis d'Arnaud collected the first multihit game of his big league career in Friday night's win over the Nationals, going 2-for-4 with a double. The rookie came into the game 3-for-28 (.107) with a double and a home run since his recent callup from Triple-A Las Vegas.

"The first week or so, I was putting too much stress on myself, I feel like," d'Arnaud said. "I just relaxed yesterday, and it worked out for me."

d'Arnaud followed that up with another 2-for-4 night in Saturday's 11-3 win over the Nationals.

Manager Terry Collins said he began seeing progress in the Mets' previous game against the Phillies, when d'Arnaud flew out to deep left and lined out to deep center in his final two plate appearances.

"I thought the last game in New York he hit the ball hard twice, very good swings," Collins said. "I thought he had good at-bats last night, so I think he's starting to settle in and put better swings on it."

On Friday, d'Arnaud ripped a double into the left-center-field gap against Washington starter Jordan Zimmermann in the fifth inning, then lined a single to left against reliever Ryan Mattheus in the ninth.

d'Arnaud, the Mets' No. 2 prospect, hit .304 with a .487 on-base percentage in 19 games for Las Vegas this season and said he's learning to deal with Major League pitching.

"Just always be ready to hit, because you never know when you'll get that mistake," he said. "You see less and less mistakes up here compared to down there. That's what I've noticed."

Worth noting

• Alderson confirmed after Saturday's game that reliever Vic Black, whom the Mets got in the Byrd trade, will join the team on Sunday, the first day of expanded rosters. He is scheduled to arrive around noon ET and should be available.

Black made his Major League debut with the Pirates at Nationals Park on July 25 and pitched a scoreless third of an inning. In three appearances for Pittsburgh, he gave up two runs over four innings.

• The Mets optioned left-handed reliever Robert Carson to Triple-A Las Vegas after Saturday's game. The 51s were on the verge of clinching a playoff berth, but Alderson said their pitching is thin and that Carson will help.

• In talking about Black's arrival, Collins quipped that, "We're playing so late at night, anybody can get in." Sunday's game starts at 8:05 p.m. ET for ESPN's Sunday Night Baseball, and the Mets then have to fly to Atlanta for Monday's 1:10 p.m. Labor Day game against the Braves.

Andrew Simon is a reporter for MLB.com. Follow him on Twitter @HitTheCutoff. This story was not subject to the approval of Major League Baseball or its clubs.