Celtic have secured the signature of Kris Commons but may face a fight to keep Emilio Izaguirre, with Aston Villa pursuing the Parkhead defender.
Commons, 27, agreed a three-and-a-half-year deal worth £20,000 a week after passing his medical in Glasgow. But while his arrival is a huge boost for manager Neil Lennon, the prospect of losing Izaguirre to the Premier League will concern the Celtic manager.
Sportsmail understands Villa boss Gerard Houllier had the Honduran international watched in the 4-0 hammering of Hearts.
The 24-year-old has made a massive impact in only five months at Parkhead and is openly being discussed by Premiership scouts - despite the attacking left-back having signed a three-year deal when he arrived from Motagua last August.
Wigan's Roberto Martinez targeted him last season and Everton boss David Moyes was also at the Hearts game, although the Goodison club are short of funds to finance any deal.
With Celtic keen to hang on to their key men as they pursue the Treble - and speculation that Paddy McCourt is also attracting interest from England and abroad - Lennon will hope that the arrival of Commons sends out another signal of the club's ambition, which may persuade his stars to stay.
A ringing endorsement of the player's ability came from Gordon Strachan after he experienced the Commons touch before departing the Middlesbrough hot seat.
'Kris is one of the best players in the Championship,' the former Celtic boss said on hearing of his £300,000 arrival from Derby County. 'I like him. He's a good player and he can go past a player or two.
'He can play anywhere across the midfield or off the front. So he is versatile - you are getting more than one player there.
'Charlie Adam and Graham Dorrans were the best players in the Championship last season and Commons is one of them this time.
Eye-catching: Emilio Izaguirre (left) has impressed since his arrival at Parkhead
'He can score spectacular goals and has a feint that takes him beyond defenders.'
Strachan's words were echoed by John McGovern, the European Cup-winning captain at Nottingham Forest who has monitored Commons' progress since his career took off at the City Ground.
'On his day, Kris is one of the best players in the Championship,' he told Sportsmail. 'Probably the only reason he is not playing with an English Premier League club is that he has lacked a wee bit of consistency.
'Kris has a terrific shot on him and he can score goals. But he's also a very creative player, he can hit good crosses and get past people in the middle of the park or out wide.'
Commons' arrival in Glasgow may have an impact on another Scottish club, with Derby lining up Kilmarnock's Conor Sammon as a replacement - after a verbal offer was made to the Rugby Park club.
The player has already turned down an approach from Scunthorpe, but may find a move to Pride Park more appealing. Celtic midfielder Marc Crosas, meanwhile, was last night cutting his ties with Parkhead as he headed for Gerona in Italy's Serie B.
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Explore more:People: Gordon Strachan, David Moyes, Gerard Houllier, Charlie Adam, Roberto Martinez Places: Glasgow, Italy, United Kingdom