Former Chelsea and Barcelona midfielder Boudewijn Zenden is being evaluated ahead of a potential move to Celtic.
The much-travelled Zenden, who has also had spells at PSV Eindhoven, Middlesbrough, Liverpool, Marseille and Sunderland, is available on a free transfer after leaving the Black Cats at the end of last season and trained with the Parkhead outfit on Saturday.
"Bolo came in a couple of days ago and he trained yesterday," Celtic assistant manager Alan Thompson told Sky Sports. "He's a free agent with an unbelievable CV. He wants to come, so we'll have a look and see what we can do."
The 35-year-old former Holland international will train with the Celtic squad over the next few days in a bid to convince manager Neil Lennon to offer him a deal.
Celtic have had more than their fair share of injuries and illness this season, with the likes of Mark Wilson, Ki Sung-yueng, Joe Ledley, Charlie Mulgrew, Mo Bangura and Glenn Loovens all sidelined, and Lennon is known to be keen to bolster his squad.