Ramsey returned to full training Monday following a five-week absence with a thigh problem and had been set to make his return to the Gunners for their trip to Southampton, where they drew 2-2 on Tuesday.
But Ramsey has sustained a fresh tendon injury rather than a setback with the previous ailment, Goal UK reports, and he is expected to be sidelined four to six weeks.
It is a blow to Arsenal's hopes of winning the Premier League title and progressing beyond the last-16 stage of the Champions League. The club faces Bayern Munich in the first leg Feb. 19 to end a demanding 11-day run of fixtures in which it also plays Manchester United and Liverpool.
Ramsey has been out of action since suffering a grade-two thigh strain in Arsenal’s Boxing Day win over West Ham.
He had been Arsenal’s top player in the first half of the season, scoring 13 goals in 26 Premier League and Champions League matches.