The Detroit Lions first preseason game brought injuries, most notably second-year quarterback Hendon Hooker went down on his second series with a concussion.

The Lions don't know when to expect Hooker to return — he must first clear medical protocol — but there's hope he could return by the end of the week.

"Yeah, honestly, we don't know where he's going to be, he's not going to be out there today," Lions coach Dan Campbell said before Sunday's practice in Allen Park. "We probably won't have him tomorrow, and it's looking less like we'll have him in practice this week until Friday. We'll get him ready for the Chiefs and that's not a guarantee until you know, he obviously clears the concussion protocol then we're on hold with him."

The Lions play in Kansas City on Saturday in their second of three exhibition games, before the Sept. 8 regular-season opener vs. the Los Angeles Rams.

INSIDER: Hendon Hooker brought a burst of light on a wet and dreary night. Then it was over.

Although Hooker's NFL debut was limited to two series, the Lions were encouraged by his performance.

"There were some encouraging things in there," Campbell said. "You know, he was able to move the offense down the field, he saw a couple of things, had a high throw, did a good job on one of his progressions kicking it out to the running back, you know, had a couple of runs there. So for the limited snaps that he was in there with a very limited package offensively, he was promising."

Concussions protocol is a slow process, and there is no timeline for a player to return when they go down with a brain injury. It could be one week, or it could be something that lingers. Campbell said there is a possibility the Lions will bring in another quarterback to fill out the roster until Hooker returns.

"We talked about that this morning," Campbell said. "That could come down to the wire, on today or tomorrow. There is a chance you know, and I think we'll have a pretty good idea this afternoon as to, do we need to go ahead and do that, just to make sure we got a guy other than Nate (Sudfeld), you know for the game."

In more injury news, defensive end Nate Lynn and offensive lineman Conner Galvin are both likely to be done for the season, Campbell said, after suffering injuries vs. the Giants.

Lynn had a sack and multiple pressures against the Giants before exiting with a shoulder issue, and Galvin left with a knee injury. Both turned out to be the worst-case scenario for player and club.

TRENDING: A couple Lions rookies stepped into the light in NFL debuts. Their head coach took notice.

The Lions placed Lynn on injured reserve Sunday and waived Galvin.

To fill those roster spots, the team signed linebacker Abraham Beauplan and offensive tackle Jamarco Jones.

This article originally appeared on Detroit Free Press: Hendon Hooker injury update: No timeline to return to Detroit Lions