JACKSONVILLE – This loss is significant.

Paul Posluszny, the Jaguars' starting middle linebacker and the team's on-field defensive leader, will be placed on injured reserve with a torn pectoral muscle. Announcing the situation on Monday, Jaguars Head Coach Gus Bradley left no doubt:

This is an important player, who played a critical role on and off the field.

And he will be missed.

"It's a big loss," Bradley said Monday afternoon, a day after the Jaguars' 24-6 victory over the Cleveland Browns at EverBank Field. "He's been playing really well lately.

"He's been playing well ever since I've been here, but I think he's really coming into his own and really understands the defense. He really takes total command of the defense. That will be a difficult one."

The news regarding Posluszny came the same day the Jaguars announced that defensive end Andre Branch will miss about six weeks with a torn groin muscle sustained against the Browns.

Branch has three sacks this season.

"It's the same situation – he's been playing really well, too," Bradley said. "Any time you have injuries with guys who are playing well it stings you a little bit."

The Jaguars activated rookie defensive end Chris Smith, a sixth-round selection in the 2014 NFL Draft from Arkansas, from the practice squad.

"He's really done a nice job," Bradley said of Smith. "If we didn't feel that way, we would have maybe looked elsewhere."

Posluszny leads the Jaguars defense with 69 tackles, and had a sack and a fumble recovery Sunday. He is third in the NFL in tackles, and also had two sacks this season. He led the team in tackles each season from 2011-2013 and was a Pro Bowl selection last season.

Posluszny re-entered the game and finished the series on which he was hurt.

"He's incredible," Bradley said, laughing. "Just his toughness and what he means to the team … it's tough, because he is talented and the captain of our team and a leader. To downplay that part of it wouldn't be fair to him.

"He's an important part, but I do believe we'll have guys step up."

Posluszny is expected to have surgery this week. Bradley said J.T. Thomas – a starter at the Otto linebacker position the last four games – likely will move to the middle linebacker spot.

"We've got some guys who will step up," Bradley said. "That's what this league's all about. I think we'll be OK."

Bradley said he doesn't anticipate the Jaguars signing a veteran linebacker, with middle linebacker Jeremiah George – signed recently from the Jets' practice squad – available and ready for an expanded role. George has been inactive on game days since signing with the Jaguars September 23.

Dekoda Watson or LaRoy Reynolds likely will play the Otto outside linebacker position. Watson was signed as an unrestricted free agent in the offseason to play the Otto, and when he missed the offseason and much of training camp with a groin injury, Reynolds started the first three games of the regular season.

Bradley said the position will be competitive this week, and that Watson has improved in recent weeks.

"He feels a lot better in his responsibility, and how he's got to go about doing it," Bradley said. "He just feels like where he's at in our system, he felt better last week than he has at any time."

Also on Monday:

*The Jaguars also announced that cornerback Aaron Colvin could practice Wednesday on a limited basis. A rookie fourth-round selection from Oklahoma, Colvin has spent the first seven games of the season on the Physically Unable to Perform list after sustaining a torn anterior cruciate ligament at the Senior Bowl in January. Once Colvin practices, the Jaguars have 21 days to move him to the active roster or end his season by placing him on injured reserve. "We'll wait and see how he progresses," Bradley said.

*Bradley said the role of rookie outside linebacker Telvin Smith could grow. He has been playing mostly in a nickel role in passing situations, but had an interception, a near interception and a sack fumble Sunday. Bradley said he has grown increasingly comfortable and could push for repetitions at weak side linebacker, where veteran Geno Hayes has started the first seven games. "He's consistently gotten better," Bradley said of Smith. "His comfort level and understanding of the defense is growing." …

 *The Jaguars announced that cornerback Alan Ball likely will not practice Wednesday after sustaining a biceps/shoulder injury Sunday.  His status for Sunday is uncertain. …

*The team announced that rookie safety Craig Loston sustained a hamstring strain Sunday, with center Luke Bowanko sustaining a sprained ankle. Loston will be evaluated later in the week and Bowanko is expected to practice Wednesday. …

*The team announced it will update the status of running back Toby Gerhart, out the last two weeks with a foot injury, on Wednesday. …

*The Jaguars also announced that tight end Marcedes Lewis is progressing well, with the first day he can return to practice being October 28. He can return to play November 23. Lewis is on the injured reserve-designated to return list with a high-ankle sprain. …