Nothing is official, but the warning signals about the condition of Lucas Duda’s back suggest the Mets are bracing for bad news when the final diagnosis is rendered Monday by Dr. David Altchek. Not only did manager Terry Collins express concern about the possibility of a long-term problem, but captain David Wright indicated the Mets don’t expect to have Duda’s services as they begin a three-game series Monday night against the National League East leaders in Washington.

Duda missed his second straight game Sunday as the Mets scored a 3-1 win over Milwaukee. He had more tests Sunday morning, and Collins said those results would be re-evaluated by Altchek.

Asked for his expectations, Collins said: “I’m real concerned. There’s no question I’m real concerned this is going to keep this guy out for awhile, but that’s just me.”

Duda declined interview requests before the game, saying he had no final diagnosis, but Wright made his loss sound like a foregone conclusion.

“We’d like to have him in the lineup for sure,” Wright said. “He’s a lefthanded power bat that fits nicely right in the middle of what we’re trying to accomplish. We’d like to get him back as soon as possible, but at the same time, you’ve got to get him healthy.

“It’s something he’s got to take care of, and hopefully, we can hold down the fort while he’s gone.”

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Harvey stays in regular slot

Since Matt Harvey last only 2 1⁄3 innings in his last start against Washington on Thursday, some thought he might move ahead of Bartolo Colon to pitch Monday night’s series opener, but Collins slotted Harvey in his regular rotation spot Tuesday. “It’s because of what he did [Saturday in a side throwing session],” Collins said. “He threw a lot of pitches. I thought he needed a second day’s rest.”

Pen dishes goose eggs

The Mets bullpen ran its scoreless streak to 14 1⁄3 innings over the past four games, thanks to solid outings by Jim Henderson in the eighth inning and Jeurys Familia, who closed. After pitching three straight days, Familia is not available Monday night, and Collins said Logan Verrett is being saved in case the Mets need a multiple-inning effort or spot start down the road.