Johnson, 27, is a former fifth-round pick of the Steelers back in 2014. He lasted just a few months in Pittsburgh before he was waived and later claimed by the Jets.
Johnson returned to the Jets last year before signing on with the Lions this past March. Unfortunately, the Lions released Johnson coming out of the preseason.
In 2017, Johnson appeared in 15 games for the Jets and was rated by Pro Football Focus as the No. 35 center out of 36 qualifying players.
Kilgore, 30, is a former fifth-round pick of the 49ers back in 2011. He has spent all seven years of his NFL career in San Francisco and was in line to be an unrestricted free agent next month.
Kilgore played out the final year of the three year, $5.25 million deal he received back in 2014 before agreeing to a three-year extension worth nearly $12 million and includes $7 million guaranteed with the 49ers during the offseason.
The 49ers traded Kilgore to the Dolphins a month later.
In 2018, Kilgore has appeared in four games for the Dolphins.