The Tampa Police Department released a statement saying a woman alleged Foster "slapped her phone out of her hand, pushed her in the chest area and slapped her with an open hand on the right side of her face," according to the ESPN.com report.
The San Francisco Chronicle confirmed with Santa Clara police that Foster and the same woman, Elissa Ennis, were involved in another domestic disturbance in October, adding:
"In that incident, a neighbor called police on Oct. 12 shortly after 11 p.m. to report a loud argument between the couple at their apartment on Carlyle Court. Police said the two had been yelling at each other 'over material found on his cell phone,' according to police Capt. Wahid Kazem.
"There were no signs of injury in the disturbance, the captain said, but officers took photographs and made video recordings."
No arrests were made.
Foster was arrested twice in less than a month after the 2017 season ended. His first arrest occurred on Jan. 12 in Tuscaloosa, Alabama, for possession of marijuana.
On Feb. 11, Foster was arrested in California for suspicion of domestic violence, threats and possession of an assault weapon.
The Santa Clara County District Attorney's Office announced on April 12 that Foster was formally charged with felony counts of domestic violence with an allegation he inflicted great bodily injury, forcefully attempting to prevent a victim from reporting a crime and possession of an assault weapon as well as a misdemeanor count of possession of a large-capacity weapon magazine.
Per Tom Schad and A.J. Perez of USA Today, Foster's girlfriend told police he punched her in the head up to 10 times and physically threw her from the house and dragged her by her hair.
Those charges were dropped in May.
Coming out of college at Alabama, Foster was named a unanimous All-American and won the Butkus Award as the nation's top linebacker in 2016.
In 10 games as a rookie last season, Foster led the 49ers with seven tackles for loss and finished second on the team with 72 total tackles.
He'd registered 29 tackles in six appearances this season before Sunday's release.