49ers put offensive tackle Trent Brown on injured reserve

The 49ers will be without Trent Brown for the rest of the season after the big right tackle was put on injured reserve with a shoulder injury that had kept him out of two of the team's last three games.

Brown injured his shoulder at the end of a Thanksgiving Day practice and missed the following game against the Seattle Seahawks. He was back the next week at Chicago and played well, but the shoulder became too painful for him in the run-up to the game against the Houston Texans, and Zane Beadles started in his place.

Brown will have surgery, which Shanahan said would bring with it a five- to six-month recovery. That means Brown could miss the 49ers' offseason practices but be back for training camp in July.

'It didn't get worse, but it just didn't go away,' Shanahan said of the tear in Brown's shoulder. 'Sometimes the pain goes away with those (injuries) and the pain ends up being OK. Some guys have them early and they never get them fixed in their career, some guys need to right away.'

Beadles will start again Sunday against a Titans team that has 20 sacks in its last three games but will be without its top pass rusher, outside linebacker Derrick Morgan, who is out with a knee injury.

Morgan usually lines up against the opponent's right tackle. The Titans, however, have plenty of other talented front linesmen, including outside linebacker Brian Orakpo, who has six sacks, and defensive tackle Jurrell Casey, who has five sacks and who will be a challenge for the 49ers' interior offensive linemen.

Brown's injury comes at a sensitive time.

A former seventh-round pick, he is signed through the upcoming season and he is a candidate to one day replace Joe Staley on the left side when Staley, 33, moves on. The 49ers must start thinking about a contract extension for Brown if they want to retain him for 2019 and beyond.

Shanahan was asked if the team was disappointed Brown didn't play through the pain of the injury and finish out the season.

'Not disappointment in him, but disappointment that he doesn't get to play with the team for the these (last) games,' he said. 'I thought he was making a lot of progress. And I think Trent has a chance to be very dominant at his position, and I think he made huge strides. By no means is he fully there. But I think he had a much better year this year than just watching him on tape the previous two years.'

Shanahan added: 'Trent's a very important part of this place and our future. When you're talking about a five- to six-month injury, that's something we want to get going (on) as fast as possible, so I fully support his decision.'

CORNER ISSUES

The 49ers' two rookie cornerbacks, Ahkello Witherspoon and Greg Mabin, are game-time decisions for Sunday's game, Shanahan said, and the team might have to promote a cornerback from the practice squad prior to the game.

Witherspoon suffered an MCL sprain in the fourth quarter against Houston. Mabin, meanwhile, strained a calf in Thursday's practice mere minutes after defensive coordinator Robert Saleh said he would see more playing time against the Titans.

Both are listed as questionable on the injury report. The only fully healthy boundary cornerback is Dontae Johnson, who was pulled from Sunday's game after enduring a rough stretch against Texans receiver DeAndre Hopkins.

The two practice-squad cornerbacks are Channing Stribling, a rookie from Michigan, and Tyvis Powell, a second-year player from Ohio State.

ET CETERA

General manager John Lynch said the 49ers would coach the Senior Bowl if asked. The annual college all-star game is held in late January in Mobile, Alabama. The staffs of the two NFL teams with the worst records — and that aren't undergoing coaching changes — usually coach the two squads.

-Tight end Garrett Celek was fined $18,231 for a horse-collar tackle Sunday in Houston.

-Titans quarterback Marcus Mariota, who is dealing with a knee injury, practiced every day this week and is not listed on the injury report.