Di Natale, 36, scored in Udinese's 1-0 win at home over cellar-dwellers Catania, and despite lasting the 90 minutes at the Stadio Communale Friuli, club medics later revealed the former Italy international had picked up an injury, with a prognosis yet to be determined.
The injury could put Di Natale's career under threat with the striker having previously claimed the 2013/14 season would be his last.
"The medicals undergone by Udinese captain Antonio Di Natale earlier today have underlined the strain to the medial collateral ligament of the right knee. The extent of the injury will be considered in the next few days," a statement on Udinese's website read.
"In the meantime, the team started training again with an anti-fatigue post-match session for those who played Catania yesterday.
"The rest of the group underwent a regular training session based on exercises of possession and brief friendly matches."
In January, Di Natale said he had decided to 'stop playing football' at the end of the season but two months later he seemed less certain.
"Will I retire in June? We'll see. For now I am useful to Udinese and my goals can still be handy," the veteran forward told Corriere dello Sport.
"I am of a certain age and cannot disguise that, but I have until June to help Udinese stay in Serie A."
Di Natale has been Udinese's leading goalscorer this Serie A campaign with 11, while he has 199 goals in 383 games for the club he joined in 2004.
Luis Muriel (four) is Udinese's next best contributor in the league this season, in an underwhelming season for the club based in Italy's north east.
Udinese sit 14th in the Italian top flight but are well clear of the drop zone - 13 points above 18th-placed Livorno with just seven league fixtures to negotiate.
