Tuesday Afternoon, the San Francisco 49ers signed quarterback Josh Johnson, and released safety Bubba Ventrone. This marked the third time since May the 49ers have signed Johnson to a contract. They initially signed him on May 14. He made the 53-man roster out of training camp, but then was released on September 20 to make room for Asante Cleveland following Vernon Davis and Vance McDonald injuries. He was signed back on September 23, then released on October 10 to bring back Kassim Osgood. He was then signed again on Tuesday.

The repeated moves have become a bit of a running joke among 49ers fans, and yet there is likely a very logical explanation for these moves. In effect, the 49ers are able to have a 54-man roster for the first eight weeks of the season. Pro Football Talk and Matt Barrows both provided helpful explanations for what this means. Additionally, several NN readers understood it as well in the comments yesterday.

The 49ers do not have a quarterback on their practice squad, so Johnson is able to serve as the scout team quarterback, while Gabbert takes backup QB snaps. Once the team gets through the practice week, they then release Johnson, and sign a special teamer, like Kassim Osgood or Bubba Ventrone. The veteran special teamer does not need the same kind of preparation time, so missing practice is not a huge deal for them. They then have the special teamer back on the roster in time for the given week's game

Why would Johnson keep coming back knowing this might happen? Well, by sticking around through the practice week, he receives a game check, even without playing the game. The game check is paid midweek, as opposed to on game day, so by sticking on the roster into Friday, he is eligible to be paid. He is signed to a 1-year, $730,000 contract, so he gets 1/17 of that ($42,941) for the week's work.

Johnson conceivably could head elsewhere after the 49ers release him, but there is probably a sufficient wink-wink, nudge-nudge type of deal in place. I don't believe it is legal for the team to have any kind of formal agreement to do this, but I'd imagine this is something that happens elsewhere around the league.

It is entirely possible Johnson gets released again later this week to bring back Bubba Ventrone. Whether he does or not, this will be able to last a couple more weeks. Prior to the October 28 trade deadline, vested veterans are not subject to waivers. If a vested veteran is released, he immediately becomes a free agent. However, after the deadline, all players become subject to waivers. That means, if the 49ers release Johnson after the deadline, any other team can claim him. There is no certainty another team would grab him, but the 49ers would not have quite the same level of certainty as they do prior to the deadline when waivers does not factor in.

This is just one of the many little roster manipulations teams have to know about in a given week. Any team can do this, but not all teams take full advantage of this option.