The 28-year-old Fells received a three-year deal that could be worth up to $7 million, according to a source. The contract includes $2 million in bonuses and guarantees, with a minimum total value of $5.25 million, the source said. It maxes out at $7 million if all incentives are reached.
The length of the deal is consistent with how the Patriots have approached free agency this year. They haven't signed a free agent to a deal longer than three years and have focused on the middle class of the roster.
Both Stallworth and Gallery received one-year deals, according to sources.
This will be the 31-year-old Stallworth's second stint in New England. He was on the 2007 Patriots team that started 18-0 before losing in the Super Bowl. He had 46 receptions for 697 yards and three touchdowns that season.
Stallworth spent the next season with the Cleveland Browns, but was suspended for the entire 2009 season after pleading guilty to DUI manslaughter charges in Miami. He was back in the NFL in 2010 with the Baltimore Ravens and played for the Washington Redskins last season.
The 31-year-old Gallery was cut by the Seattle Seahawks earlier this month. He spent just one season in Seattle, where he missed time with a variety of injuries. It started with a sprained knee suffered in the preseason and a groin injury that required surgery. Gallery started in all 12 games he played for the Seahawks.
Gallery was taken by the Oakland Raiders with the No. 2 overall pick in the 2004 draft. Prior to that draft, Patriots coach Bill Belichick was asked at a news conference who he would select if he had the No. 1 overall pick.
His answer: Gallery. Quarterback Eli Manning was eventually drafted first that year.
The 6-foot-7, 325-pound Gallery has played for the Raiders (2004-2010) and Seahawks (2011), and has experience at tackle and guard.
With Patriots starting left tackle Matt Light strongly considering retirement, according to a source, and veteran right guard Brian Waters saying after the Super Bowl that he had to weigh his football future, Gallery adds some veteran insurance up front.
Also, multiple sources said Monday night that Pro Bowl guard Logan Mankins underwent surgery to repair a torn anterior cruciate ligament in the weeks following the Super Bowl.
The surgery has altered the course of Mankins' offseason, making it highly unlikely that he will participate in spring minicamps. While Mankins hopes to be ready for the start of training camp in late July, his status is a consideration as Belichick builds the team's roster.
Fells, meanwhile, adds depth at a position where the Patriots had little in the form of insurance in 2011 -- only Rob Gronkowski and Aaron Hernandez were on the roster. Fells met with the Patriots on Monday, the source said.
Signed as rookie free agent by the Atlanta Falcons in 2006, Fells has appeared in 58 career games, totaling 88 receptions, 1,001 yards and eight touchdowns. After his stint with the Falcons and then Raiders, he started 2008 on the Tampa Bay Buccaneers' practice squad before the Rams signed him to their active roster. He spent 2008-10 with the Rams before joining the Denver Broncos in 2011.
Also on Monday, the Patriots announced the signing of defensive back Marquice Cole. The 5-foot-10, 192-pound Cole projects to help most on special teams. He finished with 11 special teams tackles last season for the Jets, and also is a gunner on the punt team.
Cole, who has also played cornerback in sub packages, was not tendered by the Jets as a restricted free agent this offseason.
The 28-year-old went to Northwestern and entered the NFL as a rookie free agent with the Raiders in 2007. He spent most of that first season with the Titans' practice squad, then joined the Saints' practice squad in 2008. In 2009, he landed on the Jets' practice squad before being promoted to the active roster in September.
With the Jets over the last three seasons, Cole played in 37 games with one start and has registered 14 defensive tackles, two interceptions with one returned for a touchdown and 45 special teams tackles.
So far this offseason, the Patriots have reached agreements with nine free agents from other teams. Stallworth, Gallery, Fells and Cole join Jonathan Fanene (Cincinnati Bengals), Steve Gregory (San Diego Chargers), Trevor Scott (Oakland Raiders), Anthony Gonzalez (Indianapolis Colts) and Brandon Lloyd (St. Louis Rams).
Mike Reiss covers the Patriots for ESPNBoston.com. Information from the Associated Press was used in this report.