Ronny Deila stressed his desire to keep Fraser Forster at Celtic following the 4-0 victory over KR Reykjavik.
Executive vice-chairman Ed Woodward insists Manchester United are ready and willing to break the British transfer record.
Defender Dale Bennett has seen his contract at Watford cancelled by mutual consent.
The Academy graduate, 23, made his Hornets debut in a League Cup encounter against West Ham in September 2008 but has failed to nail down a regular first-team place at Vicarage Road.
Bennett has made a total of 25 appearances for Watford, 16 of which starts.
He also spent time on loan at Kettering, Brentford, AFC Wimbledon and Yeovil - the latter two coming over the first half of this season.