Didier Agathe has signed a short-term contract with Aston Villa and has been challenged by boss Martin O'Neill to prove he is worth a longer deal.
Agathe had a trial with Blackburn in the summer
Agathe, 31, played under O'Neill during his five-year reign at Celtic and has agreed a deal at Villa until January.
O'Neill told Villa's website: "I think he has the talent and hunger to get in the side and do a job.
"This is a big chance and challenge for him, he's got the deal now with the chance to earn something longer term."
Agathe will play for Villa's reserves against Portsmouth on Monday night and O'Neill added: "He's not just here to make up the numbers.
"He played brilliantly for a number of years at Celtic but for whatever reason, found himself out of favour.
"That happens sometimes but Didier still feels he has plenty to offer.
"He's naturally fit and he's very quick. When his confidence is up he can run past most people.
"Now he just has to work on his match fitness."
Agathe underwent a trial at Blackburn during the summer.