While Britt was removed from the physically unable to perform list on Aug. 4, he hasn't been a full participant in practice.
"I definitely feel like I'm behind because I'm not out there with the guys getting the chemistry that I need with the quarterbacks and just with everybody on the same page with what we do," Britt said, via the Providence Journal.
Britt has been reduced to warming up with teammates and participating in individual drills. The 29-year-old then works out with the rest of the rehabilitating players.
"You never know with a hamstring. One day you feel good. Then something's in the air and [it's] popping," Britt said. "The other day, you might feel bad and it might be the fastest time you ran out there. It's really a feel thing -- day in and day out."
The Patriots' wide receiver corps has been in disarray following the departures of Brandin Cooks (Los Angeles Rams) and Danny Amendola (Miami Dolphins), and Julian Edelman set to serve a four-game suspension for violating the league's substance abuse policy.
The Patriots signed Britt in mid-December, five days after he was released by the Cleveland Browns. He had just two receptions for 23 yards while playing in three games for New England in 2017.
Britt signed a four-year contract with the Browns prior to last season but he was cut loose after recording 18 receptions for 233 yards and two touchdowns in nine games.
In 2016, Britt established career highs of 68 catches and 1,002 receiving yards to go along with five touchdowns for the Rams.
A first-round draft pick in 2009, Britt had a career-best nine touchdown catches in 2010 with Tennessee, where he spent his first five NFL seasons from 2009 to 2013.
The 6-foot-3, 223-pound Britt has 329 receptions and 32 touchdowns over nine seasons with the Titans, Rams, Browns and Patriots.