Saints will hope that their move for Celtic goalkeeper Fraser Forster is not impacted by the Scottish club's reinstatement to the Champions League.
Celtic were handed a reprieve after Legia Warsaw were punished for fielding an ineligible player in their 6-1 aggregate win over the Hoops in the third qualifying round.
Bartosz Bereszynski, who came on as an 86th-minute substitute in the Polish side's 2-0 second leg victory at Murrayfield on Wednesday, was suspended following a red card for violent conduct in last season's Europa League.
Hours before the draw for the next round was to be made, UEFA announced that Celtic had been awarded a 3-0 win in the second leg, and therefore qualified on away goals after a 4-4 aggregate result.
Celtic will now face Slovenian champions Maribor in the Champions League play-off round for a place in the lucrative group stages, although Legia have said they will challenge the decision.
Saints may be watching with interest, as they try to finalise a deal for the Bhoys' England international goalkeeper, Fraser Forster.
The club are attempting to complete a transfer for the 26-year-old, ahead of the start of the Premier League season.