With Kris Dunn down, is tanking back on for Bulls?

Maybe the tank is back on.

Thanks to a second opinion Thursday, Bulls doctors put point guard Kris Dunn in the concussion protocol, one day after he fell on his face after a dunk against the Warriors.

That means Dunn is out indefinitely and Jerian Grant will start.

“Kris is in the concussion protocol, and he’s sore,’’ coach Fred Hoiberg said Friday. “There’s no doubt about it. The thing we’re thankful for is it wasn’t worse. That could’ve been a major, major injury. Obviously, it is a significant one with the concussion. You can’t take these things lightly. But the way he fell and hit headfirst, we’re really thankful he’ll be back hopefully before too long.’’

After their afternoon practice, the Bulls left for a three-game trip, starting Saturday in Atlanta, but Dunn stayed behind.

Dunn will be under doctors’ supervision daily. If he moves out of the protocol, he’ll meet up with the Bulls on the trip.

“Once the doctors deem he’s ready to go, there’s a chance he could join us,’’ Hoiberg said. “But we’ll take it slow. And he’s in a lot of pain.’’

In his last 10 games, Dunn was averaging 15.1 points, 7.8 assists and 32.6 minutes while shooting 43 percent from the field. He was playing the best basketball of his young NBA career.

He also was getting re-acclimated to playing with Zach LaVine, who finished rehabbing from surgery on his left knee last week and had three games with Dunn under his belt.

Now the Bulls will see what LaVine can do with Grant as his backcourt mate.

“I’ve been here before, so I’m prepared,’’ Grant said. “I’ve started a lot of games in my career. I feel like the last time I started, we got a win. And I did what I had to do. So I’m prepared to do whatever we need to do to get a win.’’

Like all of his Bulls teammates, Grant has seen the replay of Dunn’s fall. He called it “tough to watch.’’

But not all of the news was bad Friday.

The Bulls met with LaVine and the medical staff and decided to increase his minutes restriction from 20 per game to about 24.

“[We’ll] see how he responds these next three games,’’ Hoiberg said. “He will start getting some fourth-quarter minutes now. We’re not going to overextend him. It’s still very early in the process as far as getting in game shape. We don’t want him to get fatigued. We’ll keep his rotation stretches short.

“But we’ll have him available some in the fourth to give us what Kris does down the stretch. Kris has been as good as anybody on our team as far as helping us close out games.

“The main concern with Kris right now is to get him better,’’ Hoiberg said. “We’re not going to mope about not having him.’’

What does this mean in the big picture?

Considering the Bulls are playing the Hawks — who have been in tank mode — the Pelicans and 76ers on this trip, one bad week and the Bulls will be right back where the front office was hoping they would be: in position for one of the top four spots in the draft.

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Email: jcowley@suntimes.com