This comes less than a week after the 49ers signed McDonald to a new five-year, $35 million extension that includes $16 million guaranteed.
McDonald, 26, is a former second-round pick of the 49ers back in 2013. He was in the final year of his four-year, $3.599 million contract and was set to make a base salary of $795,797 for the 2016 season.
In 2016, McDonald has appeared in 11 games and caught 24 passes for 391 yards receiving and four touchdowns. Pro Football Focus has him rated as the No. 20 tight end out of 63 qualifying players.
Allen, 24, signed on with the Buccaneers s an undrafted free agent out of Louisiana-Monroe back in 2014. He had a brief stint with the Packers before returning to Tampa Bay during the 2014 season.
Since then, Allen has been on and off of their active roster.
In 2014, Allen appeared in three games.