Posted by ESPN.com's Tim Graham

One week into the season, all four AFC East clubs are missing an important linebacker.

The Miami Dolphins and New York Jets opened the season each knowing they would be without a starting outside linebacker.

The New England Patriots and Buffalo Bills lost their best inside linebackers for a few weeks because of injuries suffered Monday night in Gillette Stadium.

Let's take a look at each void and who is filling it.

Mayo

New England Patriots

• Who's down? Inside linebacker Jerod Mayo.
• Why? Injured right knee.
• How long? Reportedly six to eight weeks.
• Who steps in? Gary Guyton or Adalius Thomas.

Analysis: The Patriots aren't as forthcoming with injury information as other teams, so we don't know for sure how long Mayo will be sidelined, but his absence will hurt.

The Boston Globe's Monique Walker and Christopher L. Gasper, citing two unnamed sources, report Mayo suffered a sprained medial-collateral ligament. Sources differed on the length of Mayo's recovery time, with eight weeks the longest estimate.

The Patriots turned over the defense, losing four significant leaders to retirement or trades. Mayo's importance in the transition was underscored by the fact his teammates elected him a defensive captain.

Mayo is the reigning NFL Defensive Rookie of the Year for amassing 139 tackles.

Guyton and Thomas filled in for Mayo on Monday night but were shaky.

Posluszny

Buffalo Bills

• Who's down? Middle linebacker Paul Posluszny.
• Why? Broken left arm.
• How long? Indefinitely.
• Who steps in? Marcus Buggs.

Analysis: What's up, Doc? That's what the Bills are asking because Buggs doesn't play anything like Posluszny.

The injury Posluszny suffered in the second quarter Monday night is similar to the one that ended his rookie season after three games in 2007. But this occurrence, while it will require surgery, isn't believed to be as serious. Posluszny expressed optimism it wasn't a season-ending injury.

Posluszny, the Butkus Award winner at Penn State four years ago, is a Bills captain. He led them with 129 tackles last year. He also had an interception, a forced fumble and a recovery.

It's a potentially season-changing blow to the lineup.

Pace

New York Jets

• Who's down? Outside linebacker Calvin Pace.
• Why? Suspension.
• How long? Four weeks.
• Who's in? Vernon Gholston.

Analysis: Pace is serving a four-game suspension for violating the NFL's policy on performance-enhancing substances and can't even hang out at the Jets facility.

Considering how they manhandled the Houston Texans on Sunday, the Jets did just fine without Pace and defensive end Shaun Ellis, who served a one-game suspension for getting busted with marijuana.

Gholston made four tackles, including one for a loss, but he's not even close to the player Pace is. Pace was a hellion last year, recording seven sacks, 12 tackles for losses and five forced fumbles.

The Jets proved they can make so without him, but they'll be even scarier when he returns.

Roth

Miami Dolphins

• Who's down? Outside linebacker Matt Roth.
• Why? Groin -- we think.
• How long? Six weeks.
• Who's in? Jason Taylor.

Analysis: This is the least significant of the four situations because Roth wouldn't have been an every-down player anyway, and his replacement is one of the greatest defenders in team history.

Roth, last year's starter on the strong side, arrived at training camp with what was first called an illness but was later classified a groin injury. He also wanted a new contract. Regardless, he didn't practice with the team. The Dolphins placed Roth on the injured list, meaning the soonest he must sit out the first six games.

The intention when Taylor signed with Miami was to use him on passing downs. Now the 35-year-old is playing almost every down. He recorded a sack in the season opener.