The Seahawks added quarterback Tarvaris Jackson to their roster Friday, a day after it was announced he had agreed to terms.

To make room for Jackson on the 90-man training-camp roster, the Seahawks cut quarterback Jerrod Johnson, a first-year player from Texas A&M who had signed in April. That leaves Seattle with three quarterbacks, starter Russell Wilson, Jackson and Brady Quinn.

Seahawks coach Pete Carroll said Thursday that Jackson and Quinn will battle for the backup spot. Jackson, though, figures to have an edge after starting 14 games for the Seahawks in 2011 and having a familiarity with the playbook and most of the players.

Mansperger dies

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Dick Mansperger, the team’s first director of player personnel, died in May after a long battle with cancer, according to the Seahawks’ website. He was 80.

According to a story on the team’s site, Mansperger was one of the first hires made by the Seahawks and served as the director of player personnel from 1976 to 1983. Among other signings, he was given credit for bringing in free-agent quarterback Dave Krieg, who played 12 seasons for the team and remains second in franchise history in passing yards at 26,132 behind Matt Hasselbeck.

Bob Condotta: 206-515-5699 or bcondotta@seattletimes.com. On Twitter @bcondotta.