Zack Wheeler of the Mets stands on the mound in...

Zack Wheeler of the Mets stands on the mound in the second inning of a game against the Oakland Athletics at Citi Field on Wednesday, June 25, 2014. Credit: Jim McIsaac

Zack Wheeler's outing was finished before the sun had set over Citi Field, after only two innings in which the A's laced liners all over the field.

Sure, his fastball found too much of the plate and his breaking pitches were flat, but Wheeler suspected there was another reason why he endured the shortest -- and worst -- outing of his career.

He believes the A's were stealing signs.

After the Mets' 8-5 loss Wednesday night snapped their three-game winning streak, Wheeler said the A's had too many good swings off pitches when they had a runner on second base. That led him to believe the guys on second were peeking in at Travis d'Arnaud's pitch-calling.

"I'm pretty sure they had my signs when they were on second,'' Wheeler said. "That's my fault for not picking that up earlier.''

Wheeler (3-8, 4.45 ERA) gave up six runs and six hits. He pointed specifically to when Coco Crisp managed to hit a 95-mph fastball on the outer half of the plate into centerfield for an RBI single in the second.

There were runners on first and second with one out at the time of Crisp's hit.

"When somebody turns on a 96-, 97-mph inside fastball at their knee on the corner, you sort of get a feeling,'' Wheeler said. "Hitting a few pitches like Crisp did, balls down in the zone, out and away, and he hits it back up the middle, I'm like, 'Uhhh.' ''

When Wheeler's sign-stealing accusation was relayed to Crisp, he said, "We don't do that over here.''

Crisp's hit gave the A's a 3-0 lead, and they already were well on their way to ending Wheeler's night early. Brandon Moss hit a moonshot of a two-run home run in the first inning, depositing a 2-and-0 changeup into the top rows of the second deck in rightfield.

"I haven't seen him get hit that hard, probably ever, to be honest,'' manager Terry Collins said.

But Wheeler was bothered that he didn't stop the damage, and he believes he would have been in a better position to do so had he changed his signs earlier.

After Crisp's RBI single that first raised Wheeler's suspicion, pitching coach Dan Warthen came out to the mound to give him a breather, to no avail.

Wheeler walked John Jaso to load the bases, and Yoenis Cespedes hit a hanging curve over the middle of the plate into the leftfield corner for a bases-clearing double.

With Moss up, Wheeler called d'Arnaud to the mound to discuss his sign-stealing theory. Whatever change they made then with their signs, Wheeler believes it worked.

"After that, the next few pitches were good,'' he said.

Wheeler struck out Moss and Josh Donaldson to end the inning, stranding Cespedes on second. But the damage was already done, and the Mets were in too big a hole to climb out of.

A pinch-hit, three-run home run by Lucas Duda in the seventh and a two-run shot by Chris Young an inning later cut an 8-0 deficit to 8-5, but they couldn't get any closer.

This was certainly not what the Mets had in mind for Wheeler, who was coming off a three-hit, eight-strikeout shutout in Miami. Collins spoke optimistically before the game about that gem serving as a steppingstone for the hard-throwing righthander. But Wheeler said he's not fretting.

"I'm already over this, to be honest with you,'' he said. "Forget it and move on.''