The Chargers placed a first- and third-round tender on Sproles last month, shortly after they released starting running back LaDainian Tomlinson. At first, it was believed that the team wouldn't tender Sproles, making him an unrestricted free agent, but Chargers general manager A.J. Smith said "we decided that in the best interests of the Chargers, that this is what we're going to do."
Sproles' agent, Gary Wichard, told The Associated Press at the time that he hoped the sides would work out a long-term deal. That hasn't happened yet.
The Chargers tagged Sproles as their franchise player after the 2008 season and paid him $6.6 million. He responded by posting career highs in rushing yards (343), receiving yards (497) and total touchdowns (seven) last season.
With Tomlinson gone, Sproles could be the Chargers' starting running back, although the team has seemed reluctant to go that route. They value the five-year pro as a multiple threat who also can catch passes out of the backfield and return punts and kickoffs.
Marcus Mason, whose 32 career carries all came last season with the Washington Redskins, is the only other Chargers running back with NFL regular-season experience. That has led to some speculation that San Diego is seeking a running back in this month's NFL draft.
The Associated Press contributed to this report.