The team traded for linebacker Rolando McClain on July 1 to help replace him.
Flowers visited the Chargers last week and drew interest from numerous teams after he was released by the Chiefs earlier this month. Flowers, originally selected by Kansas City in the second round of the 2008 NFL Draft, made his first Pro Bowl last season but the Chiefs let him go in part because he of his $10.5 million salary-cap hit in 2014.
Flowers, 28, provides the Chargers with much-needed depth. The team reportedly signed him to a one-year deal, which is a low-cost move for them while allowing Flowers to prove he is worth another long-term, big-money contract next offseason.
The report says Beason suffered a sesamoid fracture in his right foot, per a source aware of the diagnosis. He's expected to miss 12 weeks, which puts Beason out for most of training camp and threatens his availability for Week 1.
Rookie Devon Kennard would handle middle linebacker duties if Beason is out for any regular season action.
"During Sean's run today with our medical staff, he suffered an injury," coach Mike Smith said in a statement. "We sent Sean to the doctor for some additional testing and evaluation and unfortunately the results showed that he ruptured his Achilles tendon. Sean had been working extremely hard to get back on the field, but regrettably he will miss the entire 2014 season. He will have a procedure done in the near future and we expect him to make a full recovery."
Weatherspoon is entering the final year of his contract and will be a free agent after this year.
ESPN.com reports Tuesday Lee has been diagnosed with a torn ACL in his left knee, an MRI confirmed. If the report is accurate, Lee will need surgery to repair the knee, which would force him to miss the upcoming season.
The typical recovery timeline for ACL surgery is typically 9-to-12 months. Lee suffered the injury during practice Tuesday.