PHILADELPHIA — The Eagles will be without the anchor of their offensive line for at least a month and possibly for the rest of the season.

Center Jason Kelce will miss at least 4-6 weeks after suffering a torn medial collateral ligament and partially torn anterior cruciate ligament in his right knee during a 24-23 victory over Baltimore on Sunday.

Eagles head athletic trainer Rick Burkholder explained that Kelce will undergo an arthoscopic procedure today in which orthopedic specialist Dr. Peter DeLuca will determine the extent of the damage to the ACL. If the tear is not too severe, it is possible he could be fitted with a brace and play again this season once his completely torn MCL heals. The other option would be for Kelce to have reconstructive surgery, which would sideline him for the rest of the season.

“We’ll share this information with other sports medicine experts around the country, some of the physicians in the National Football League, and then we’ll have a better idea of the treatment plan,” Burkholder said Monday. “As far as we can tell right now, it’s a mixed bag. Some people get it fixed right away and other people just let the MCL heal and play with the partial (tear of the ACL).”

Kelce, a sixth-round draft pick in 2011, started every game last season and was considered a potential Pro Bowler this year. He was hurt in the third quarter against the Ravens when safety Ed Reed hit his leg.

Former practice squad member Dallas Reynolds replaced him and played well. He was on the field for the Eagles’ final two touchdowns, including quarterback Michael Vick’s 1-yard run with 1 minute, 55 seconds left in regulation.

Reynolds make his first career start for next Sunday’s game against the Cardinals in Arizona and for the foreseeable future.

“Dallas did everything that Jason was doing with the calls,” Eagles coach Andy Reid said Monday. “He’s a smart kid. He had a big challenge (against the Ravens), literally, physically and mentally, but he held his own there. He played good, solid football.

“His situation is one of the good stories in this game. He has an opportunity now and he’s got to make sure he handles it the right way and continues to work hard. You don’t forget what got you there.”

It took a while for Reynolds to get there.

The 28-year-old signed with the Eagles as an undrafted free agent out of Brigham Young University, Reid’s alma mater, in 2009 and then spent three seasons on the practice squad. The Eagles promoted him to the active roster for one game as a rookie but he was deactivated. Because players are limited to three years on an NFL practice squad, Reynolds had to either make the active roster this season or get released.

“(Giving up football) was something that plays on your mind from time to time, but it wasn’t something I really thought about,” Reynolds said Monday. “I just focused on trying to get better and doing my best every day.”

Sunday’s game marked the first time he had played center in a regular-season game on any level. Like his older brother Lance, Jr. and younger brothers Matt and Houston, he was a tackle at Timpview High School in Provo, Utah, and at BYU. Lance Jr. spent some time with the Seattle Seahawks, Matt is on the Eagles’ practice squad and Houston is a junior at BYU. Their father, Lance, is an assistant coach at BYU, where he also coached Reid.

Since the preseason ended, Dallas Reynolds had served as the center on the scout team, running the opposing team’s offensive plays against the Eagles’ defense in practice. But he still studied the Eagles’ playbook and paid attention in position meetings just in case he was called upon.

“(Replacing Kelce on short notice) was as tough as I thought it was going to be,” Reynolds said. “I think it helped that I really didn’t have time to think about it. There were a few butterflies, but I didn’t have time to be nervous. I took a few practice snaps and then I was in the huddle.”

The Eagles are expected to sign another center. Steve Vallos and Julian Vandervelde, who were with the Eagles during training camp and the preseason, are the leading candidates. They could also call Jamaal Jackson, who is now a free agent after spending nine seasons (2003-2011) with the Eagles. He was Kelce’s backup last season.

But whomever they sign will be Reynolds’ backup. Reynolds will be the starter as long as Kelce is sidelined.

“I’ve been looking forward to this moment for a long time,” said Reynolds, who is married (Suzanne) and has a 2-year-old daughter (Sharae). “I’m excited about this opportunity.”

Extra points: Safety Nate Allen (shoulder contusion), safety Colt Anderson (hyperextended knee), defensive end Jason Babin (abdominal strain), tackle King Dunlap (strained hamstring) and wide receiver Jeremy Maclin (hip contusion) were hurt against the Ravens. Dunlap and Maclin are not expected to practice Wednesday. If Dunlap cannot play against the Cardinals, Demetress Bell will start at left tackle against the Cardinals.

Six of the Eagles’ defensive backs — Anderson, Brandon Boykin, Kurt Coleman, Curtis Marsh, Dominique Rodgers-Cromartie, David Sims — will attend the ConKerr Cancer’s pajama party today at 6 p.m. at the Children’s Hospital of Philadelphia. The players will wear their pajamas and help children on the Oncology floor sew pillowcases at the Ronald McDonald Family Room at CHOP.

Contact David Weinberg:

609-272-7186