The goalkeeper (24) did not play a first-team game for former club Newcastle and signed for £2m after two loan spells at Celtic.
The Wales defender (20) joined on a free transfer from Cardiff in 2011. A right-back by trade, he was switched to the left on Wednesday because of injuries.
A Swedish defender (25), he rose to the challenge of dealing with the threat from Andres Iniesta. He joined last January from Rosenborg.
The Nigerian centre-half (24) is now a regular after signing this year from Israeli side FC Ashdod.
After struggling in his first season at Celtic, the centre-half (26) is now a regular. He joined from Nottingham Forest on a free transfer in 2011.
The midfielder (26) was manager Neil Lennon's first signing in 2010 and is a set-piece specialist.
The Welsh midfielder (25) spent six years at Cardiff before Celtic beat off competition from Stoke City and West Brom to sign him on a free transfer in 2010.
A bargain £900,000 signing from Belgian side Beerschot AC in 2011, the Kenyan midfielder (21) is now Celtic's most valuable asset.
The winger (29) joined for £300,000 from Derby in 2011 and has become first choice on the right side of midfield.
Nicolas 'Miku' Fedor (27) has joined on a season-long loan from Spanish club Getafe. He is valued at around £8m.
Unable to hold down a
place at Manchester
City, the Greek striker
(27) joined Celtic for
around £2m back in 2008.
An 18-year-old striker, who came off the bench to score against Barcelona, he was signed from Airdrie for £50,000 last January.