Alexander underwent an additional follow-up surgery to repair the right knee in January, U-T San Diego's Michael Gehlken reported Thursday, citing sources.
The receiver has a history of knee troubles, undergoing at least five surgeries on his left knee dating to his college days.
Alexander is an impending free agent. The additional surgery will put his readiness for training camp in question, and his chances of sticking with the Chargers appear "unlikely," according to Gehlken.
Alexander entered 2013 slotted as the Chargers' No. 1 receiver after emerging as an impact player down the stretch run of 2012. In just 10 games, Alexander nabbed 37 receptions for 658 yards and seven touchdowns.