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The club had tried desperately to sign the 22-year-old before Monday’s 11pm transfer deadline, rushing him up to Glasgow at the last minute, but part of the paperwork arrived just after midnight.
However, an appeal by the SFA to the world’s governing body eventually proved successful, with the youngster now getting the chance to earn regular first-team minutes north of the border, as he bids to prove his Premier League credentials.
Guidetti has struggled to make his mark at City since arriving from local club IK Brommapojkarna in 2008, but did enjoy a previous loan spell with Dutch side Feyenoord during the 2011-12 campaign, scoring 20 goals in 23 Eredivisie games.
However, after a goalless spell at Stoke during the second half of last season under former boss Mark Hughes, his Celtic stint will be a crucial one towards determining his future.
Guidetti had earlier been named to the club’s 25-man Premier League squad, along with unwanted duo Scott Sinclair and Matija Nastastic.
Manuel Pellegrini made it no secret this summer that he was attempting to ship the pair out, along with Fiorentina-bound Micah Richards and the Swede, but both will now get the chance to fight for a first-team place until at least the opening of winter transfer window.
Meanwhile, Sergio Aguero was on target as Argentina beat world champions Germany 4-2 in Dusseldorf on Wednesday night, but it was an injury to Pablo Zabaleta which was the major talking point.
The full-back limped off in the second-half after coming up on the wrong end of a Lukas Podolski challenge, having started in defence alongside teammate Martin Demichelis.
It remains to be seen what the diagnosis is, but the club at least have a suitable replacement lined up should there be any serious issue, with the summer investment in Bacary Sagna looking somewhat wiser.
There’s been better fitness news elsewhere, however, with captain Vincent Kompany overcoming a recent calf injury to start Belgium’s Thursday evening friendly against Australia.