Jonathon Niese had just been traded from the Mets to the Pirates last offseason for second baseman Neil Walker. But before he could be fitted for his new uniform, the lefthander took a shot at his former team, criticizing the defense that was played behind him.

Now he must mend some fences. In a swap of headaches, the Mets reacquired Niese on Monday in exchange for disappointing lefty reliever Antonio Bastardo, who pitched for the Pirates last season.

“I think there will be some things that will be addressed,” Terry Collins said of Niese. “There’s still some guys who are still here from last year.”

Niese, 29, posted a 4.91 ERA in 23 games (18 starts) in his first season with the Pirates. He had been bumped from the starting rotation and relegated to the bullpen, as he was late last season with the Mets.

Bastardo, 30, posted a 4.74 ERA in 41 appearances after signing a two-year, $12-million deal. He was expected to pitch in high-leverage situations but was limited to mop-up duty.

With a tight market for pitching, the Mets had resigned themselves to the potential of a reunion with Niese, who will work out of the bullpen. But Sandy Alderson said Niese also could provide “protection” to a starting rotation that has been slammed by injuries.

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The Mets can control Niese through 2018 with a $10-million option for next year and an $11-million option for the following season.

Making progress

Zack Wheeler will begin his minor-league rehab assignment on Saturday, a major step in his comeback from Tommy John surgery. Alderson said Wheeler hit 91-93 mph during a simulated game Monday. It was the first time he faced batters since undergoing surgery in March 2015.

Injury updates

Yoenis Cespedes (quadriceps) will not be in the starting lineup Tuesday night but is expected to be available to pinch hit.

Mets videos

Asdrubal Cabrera is expected to be placed on the disabled list Tuesday with a strained patellar tendon in his left knee. The Mets promoted Matt Reynolds from Triple-A Las Vegas, and he went 2-for-4 with a go-ahead three-run homer Monday night.

Newly acquired centerfielder Justin Ruggiano left Monday night’s game with a mild strain of his left hamstring. He is expected to land on the DL. Ruggiano injured himself while legging out a grounder in the third.

Extra bases

While the Mets’ infield depth has taken a hit with Cabrera and Jose Reyes nursing injuries, Alderson said the Mets did not pursue infielders before the trade deadline. He did not rule out a reunion with infielder Juan Uribe, who was designated for assignment by the Indians . . . Pitcher Steven Matz pinch hit and drew a walk . . . The Mets received multiple trade inquiries about 17-year-old shortstop prospect Andres Gimenez, according to sources. But the Mets refused to move Gimenez, who signed a $1.2-million bonus as a 16-year-old last summer.