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6/8/2013 8:58 P.M. ET

Mets designate Ankiel, will call up Nieuwenhuis

NEW YORK -- Rick Ankiel has been designated for assignment by New York after going 0-for-4 with three strikeouts in the Mets' 2-1 loss to the Marlins on Saturday. Kirk Nieuwenhuis, who's batting .232 with Triple-A Las Vegas this season, will replace the outfielder.

Ankiel came in as a pinch hitter and defensive replacement in the Mets' 20-inning marathon and failed to record a hit as New York's offense faltered in extra innings. He's batting.188 this season (24-for-128), just .098 (8-for-82) since debuting with New York on May 2 and only had two hits in his last 35 at-bats.

He played 21 games with the Astros this season before joining the Mets and has struck out 60 times this season.

Nieuwenhuis has struggled at Triple-A, even in the hitter-friendly Pacific Coast League, but he has hit 10 home runs and batted .252 in 91 games with New York last season. He was just 2-of-16 in 13 Major League games this year.

Harvey exits early with lower back tightness

NEW YORK -- When Matt Harvey finished up his seventh inning, he felt some tightness in the right side of his lower back. When he went out to hit in the bottom of the frame, he thought it would loosen itself back up -- he even singled during his at-bat.

When he came out to warm up for the eighth, a crowd gathered around the starting pitcher. Manager Terry Collins was there. So was trainer Brian Chicklo. Moments later, Harvey walked to the dugout. His day was done because of lower back tightness.

"I was fine to pitch," Harvey said after the game. "I could've obviously stayed out there, but obviously risking more injury would be not good."

Harvey earned another no-decision, but his seven innings of one-run, six-strikeout ball further bolstered his already stellar Cy Young-worthy resume. He entered with just a 4.25 ERA against the Marlins, but until exiting an eventual 2-1, 20-inning loss, Harvey was spectacular.

He said he's fine to make his next start, whether it is on Thursday or Friday.

"I think the sixth and seventh were my best two innings, and it's frustrating coming out of the game when you're finding your rhythm," Harvey said.

He'd experienced a similar injury a handful of times in college, and on Saturday the training staff found a way to help it right away. He wasn't sure how to describe the procedure used, but the chiropractic method realigned his hips and had him feeling fine even before the marathon game ended.

Next time it could be something used between innings, he said, so that he can stay out on the field.

But once Harvey alerted Terry Collins, the manager knew it wasn't worth taking the risk of leaving his ace out on the mound. Harvey usually has no problem pitching through adversity, so when he told Collins of the tightness it meant that it was something to note.

"My goodness gracious," Collins said, "if there's anyone that we don't need hurt it's Matt Harvey."

Aardsma posts scoreless frame in big league return

NEW YORK -- David Aardsma joined the Mets on Saturday to bolster a bullpen that entered Saturday's game with a 4.91 ERA, as well as failing to convert save opportunities at a nearly 50-percent rate.

New York's newest relief pitcher didn't take long to make his presence felt. He threw a 1-2-3 12th inning in the Mets' 2-1, 20-inning loss to the Marlins on Saturday, striking out one and clocking 92 mph on Citi Field's scoreboard radar gun.

Aardsma said it "absolutely" feels great to be back in the Majors. "I feel good," is the phrase that frequently emanated from around his locker on his first day with New York, and words that he put on display on Saturday.

The Mets optioned relief pitcher Collin McHugh to Triple-A Las Vegas to make room for Aardsma on the active roster and transferred relief pitcher Jeurys Familia to the 60-day disabled list to open up Aardsma's spot on the 40-man roster.

Aardsma showed signs that he could be more successful in the Majors than much of New York's scuffling bullpen, posing a 2.05 ERA with three saves and 11 strikeouts over 22 innings in the hitter-friendly Pacific Coast League.

"If you can pitch there," Aardsma said before Saturday's game, "you can pretty much pitch anywhere."

Aardsma was one of the last men that Terry Collins turned to out of the pen -- only Robert Carson outlasted him in the Mets' bullpen -- but in a 20-inning marathon, New York's manager had no choice.

But Aardsma performed admirably, albeit against a Miami team that entered with the worst offense in baseball.

Aardsma's arrival immediately made him one of the team's most experienced relief pitchers. He's one of the few Major Leaguers familiar with that type of a marathon -- he said he'd been part of an 18-inning game before -- and he saved 69 games in two seasons with the Mariners before Tommy John derailed his career. His 14-pitch inning on Saturday was just his second since 2010.

With the Mets, it has a chance to be the first of many as he searches for his first firm Major League role since he was playing in Seattle.

"I feel good," Aardsma said. "I feel very good. I'm very happy with my body. It's been a long road, but it's worth it."

David Wilson is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.