The Chargers also made the surprising move of releasing veteran defensive tackle Jamal Williams.
A week ago, the team said it would not tender Sproles, allowing him to become a free agent. On Thursday, the Chargers decided they couldn't afford to lose Sproles after releasing LaDainian Tomlinson.
Sproles would earn $7.29 million in 2010 if he signs the tender. The Chargers would have seven days to match an offer if a team tries to sign him.
If it doesn't match, San Diego would receive a first- and a third-round draft choice from the team that signs him.
Last year, the Chargers kept Sproles by placing the franchise tag on him at $6.6 million.
Williams has been one of San Diego's key run-stuffers for 12 seasons. He sustained a triceps injury in the 2009 season opener and missed the rest of the year. He also has a history of knee injuries.
Backup running back Michael Bennett also was released, leaving the Chargers thin at that position. LaDainian Tomlinson was released last week after a brilliant nine-year run with the Bolts. The Chargers are expected to take a running back high in the draft.
Later Thursday, the Chargers reached a deal in principle with the New York Jets to trade cornerback Antonio Cromartie. The Jets confirmed the deal. It includes a 2011 third-round draft pick that could turn into a second-round pick, sources told ESPN's Adam Schefter.
John Clayton covers the NFL for ESPN.com. The Associated Press contributed to this story.