The Republic of Ireland and Southampton are waiting to learn the extent of the hamstring injury suffered by striker Shane Long against Inter Milan on Thursday.
The Tipperary man pulled up three minutes into the second half of Saints' 1-0 Europa League defeat at the San Siro and had to be replaced by Charlie Austin.
Manager Claude Puel has yet to discover how serious the problem is, but he confirmed Long will not be available for Sunday's trip to face Manchester City in the Premier League.
"Shane Long will be out with his hamstring injury," said the Frenchman.
"I don't know for how long at the moment, I will have a look but I don't know the timescale of the injury."
Martin O’Neill will be monitoring the situation closely as his Ireland side travel to Vienna to face Austria in a World Cup qualifier on 12 November.
A prolonged absence for Long at club level could lead to a run of games for Jay Rodriguez.
The former Burnley forward insisted his fitness was not a concern after passing up the chance to give Southampton the lead in Milan.
The 27-year-old was put through on goal after nine minutes, with the score at 0-0, but hesitated before losing possession when well placed to score. He demonstrated a similar lack of confidence later on, and was substituted as Saints fell behind.
Rodriguez is back making regular appearances having suffered anterior cruciate ligament damage in 2014.
The result meant that Southampton slipped to third in Group K.
It also gave Inter their first points of the competition and left the pool wide open when the Italian side - who visit St Mary's in a fortnight - had been at risk of elimination.
