By Dan Durkin-

(CBS) The Bears announced a series of roster moves Tuesday as they begin preparations for their Monday night matchup against the New York Jets. Here are other notes from Halas Hall.

Special teams shakeup

Chicago coach Marc Trestman expressed disappointment in the performance of his special teams unit after their poor showing in San Francisco. A blocked punt set the 49ers up with a short field to start the game, and the return game has been a non-factor.

“In the first week, we had a very good start to special teams, it didn’t work out that way this week,” Trestman said. “I think we made a number of mistakes. It started with the blocked punt. We lost contain at times, we had some double-team issues, some decision-making issues by a very young group. We’ve got to back to work, certainly. We’ve got to continue to teach and get a very young group of young players better.”

Through two games, field position has been a struggle for the Bears. Offensively, their average starting field position has been the 19-yard line, which is the third-worst mark in the league. Defensively, opponents’ average starting field position has been the 34-yard line, which is the sixth-worst mark in the league.

Judging by the comments Trestman made about returner Senorise Perry and the roster moves made today — in particular activating Rashad Ross — a shakeup at kick returner seems inevitable.

“We’re going to evaluate that (Perry as the primary returner) over the next couple of days and see where we are roster-wise,” Trestman said. “I think he’ll be back there in some fashion. We’ll make a decision as we move into Thursday and Friday, at which position back there that he’ll be at.”

Secondary without Tillman

The Bears promoted from within at cornerback, signing Isaiah Frey off the practice squad. Frey played the nickel corner role throughout the 2013 season, but he was made expendable when the team drafted Kyle Fuller in the first round. With Charles Tillman lost for the season to a right triceps injury, Fuller will now move to the outside permanently, creating an opportunity for Frey to once again play in the slot.

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Despite being unavailable on the field, Tillman will have an open door at Halas Hall any time, Trestman said.

“This building will be open to him to help us in any way he would like to do that,” Trestman said. “That will be up to him on how much involvement he wants to have.”

Defensive end rotation

The pass rush came to life against the 49ers, as the Bears leveled their rush inside and out. Through two games, defensive end Willie Young has been the Bears’ most productive defensive lineman, registering three sacks.

With five new players on the front, it will take time to figure out how everyone fits together. But the coaching staff feels it’s getting closer to finding an optimal rotation to maximize the effectiveness and skill set of the group while preserving their legs for the season.

“Well, he (Young) had 17 (snaps) in game one, we tried to get him up to about 40 this week, I think we were close to 40,” Trestman said. “We’re getting to a place where we think we’re going to have a pretty good rotation with the three guys, which is going to not only to allow them to have their legs as the season progresses and we feel good about that, and then they can have a little bit of an opportunity to rest at some point in time during the course of the game.”

Dan Durkin covers the Bears for CBSChicago.com and is a frequent contributor to 670 The Score. Follow him on Twitter at @djdurkin.