Taj Gibson on the shelf for at least four months after left ankle surgery

There goes another trade chip.

And an important one.

The Bulls announced Friday that reserve big man Taj Gibson underwent an arthroscopic repair of his left ankle Tuesday in Indianapolis.

The team said the surgery was expected and Gibson already has started the rehabilitation process, which will keep him from full basketball activity for the next four months. That means Gibson is expected to miss at least the first half of training camp and could miss the start of the season.

The 29-year-old has been hampered by ankle problems the last few seasons. They were a big issue throughout this past season. Gibson missed 20 regular-season games, 17 because of his left ankle.

After finishing second in voting for Sixth Man of the Year in 2013-14, Gibson averaged just 10.3 points and 6.4 rebounds in the regular season. He all but disappeared in the playoffs, averaging just 7.4 points and 5.5 rebounds in 12 games.

In the 2013-14 postseason, Gibson averaged 18.2 points, 6.2 rebounds and 2.4 blocks.

There was speculation the Bulls would try to move Joakim Noah or Gibson this offseason to free up salary-cap space, but with Noah’s left knee an issue and Gibson on the shelf, the Bulls might be held hostage by their own training room.

Considering they’ll be right against the cap -— and that’s with Mike Dunleavy testing the free-agent market — the hope was the Bulls could add an experienced wing by moving Noah or Gibson. It didn’t matter whether that meant bringing back Dunleavy and still having enough to add a veteran backup point guard or using all of the space on a small forward. The Bulls wanted some flexibility.

Gibson’s injury has put that plan in jeopardy, meaning there will be more pressure on Doug McDermott to make a huge jump this summer and on Nikola Mirotic to show that he can play small forward with more consistency than he did during his rookie year.