Antrim defender Aaron Graffin could be sidelined for up to five months after dislocating a kneecap in Sunday's Leinster SHC defeat by Westmeath.
Play was delayed for 10 minutes at Cusack Park as the Cushendall player received treatment for the injury.
"The pain was instant - I've never experienced anything like it," Graffin told the Irish News.
The Saffrons need to beat Carlow on 24 May to retain hopes of qualifying for the quarter-finals.
Defeat by Carlow in their next fixture could condemn Kevin Ryan's side to the Christy Ring Cup next year, just weeks after their relegation to Division 2A.
Antrim started the four-team round robin series with an impressive 5-17 to 3-22 victory over Laois before going down 1-21 to 0-7 against Westmeath.
The winner of the group will face Offaly in the Leinster quarter-finals with the second-placed team playing Wexford.
Whoever finishes bottom of the series faces a play-off against the Christy Ring Cup winners for the right to play in the Liam McCarthy Cup next year.