It looks as though Southampton will be without defender Toby Alderweireld for up to four weeks, per Sky Sports, after he injured his hamstring against Manchester United this past weekend.
Alderweireld also posted the following to Twitter:
Alderweireld has been excellent for Southampton this season, starting 16 Premier League matches and notching a goal and a solid 7.15 average match rating from WhoScored.com. His absence leaves a pretty big hole in central defense for the Saints.
With Maya Yoshida also away at the Asian Cup, Southampton's depth in defense has become pretty shallow. Manager Ronald Koeman addressed that fact, via Sky Sports:
I don't know (if we need to sign another centre half), we have to speak about that. We know that Maya will be away for some weeks, we know that. We knew already if we get some injuries then maybe it can be a problem but I think in our squad we can do some changes in positions to keep going.
Southampton are currently third in the table and have beaten Arsenal and Manchester United in consecutive Premier League matches, so the last thing the club wants is to lose the momentum it has built. It would be surprising if the Saints didn't dip into the transfer market to add some depth in the absence of Alderweireld, who they will hope will be back sooner than the four-week prognosis.