Backup quarterback Charlie Frye also signed his tender as the Raiders started getting their restricted free agents under contract for next season.
Gradkowski replaced Russell as Oakland's starting quarterback midway through last season. He provided an immediate spark, leading Oakland to comeback victories in two of his first three starts.
He got hurt midway through his fourth start, suffering a torn medial collateral ligament in his left knee and a partially torn MCL in his right knee and did not play the rest of the season.
Gradkowski completed 54.7 percent of his passes with six touchdowns and three interceptions on the season.
Russell was expected to join the team for the voluntary offseason workouts later Monday, a person familiar with his plans told The Associated Press on condition of anonymity. The person asked not to be identified because neither the Raiders nor Russell planned to make the information public.
A Raiders source told NFL.com that Russell has been working out at the training facility Athletes' Performance in Tempe, Ari. He completed 48.8 percent of his passes, with three touchdowns, 11 interceptions and a 50.0 passer rating that was the lowest in the NFL in 11 years before losing his job to Gradkowski.
Condo, who made his first Pro Bowl last season as the long snapper, will make $1.684 million next season.
Frye started the final three games last season, completing 60.9 percent of his passes with one touchdown and four interceptions. He will be paid $1.226 million next season.
The Associated Press contributed to this report