Teams that bring free agents in for visits are often updating their emergency lists.
Null was a sixth-round draft choice of the St. Louis Rams in 2009. He played in college at West Texas A&M.
In four games last season, Null was 73 of 119 for 566 yards, with three touchdowns and nine interceptions.
The Patriots have just two quarterbacks on their active roster -- Tom Brady and Brian Hoyer. They were one of just nine teams to have just two quarterbacks on their initial 53-man roster.
The Patriots also don't have a quarterback on the practice squad, and Null does have practice squad eligibility.