Maik Nawrocki has yet to make his debut for loan club Hannover 96 this season.
The centre-back joined the Bundesliga 2 side on loan back on July 5, but has yet to taste any first-team action for the German club.
Nawrocki, 24, had to overcome an injury issue after making the switch to Hannover in the summer, but has not featured for the club since making his return.
The Polish defender was not part of the matchday squad for the first four matches of the league season and also missed a first-round cup defeat to Energie Cottbus.
He had stepped up his return by playing in a bounce game for Hannover against Hamburger SV earlier this month.
The stopper played 45 minutes in the friendly match before being withdrawn at the interval in the 3-1 victory.
Manager Christian Titz said of the performance: "The way we played from the start was very positive—both against and with the ball.
"Defensively, we were also solid. The guys who had a bit less playing time recently played with great commitment.
"I liked everyone who played today. We deserved to win today."
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Since then, Nawrocki has been named on the bench for Hannover in the Bundesliga 2 but hasn't been called into action.
He was an unused substitute in a 3-0 loss to Hertha BSC, a 2-2 draw with Dynamo Dresden and for the 3-1 win over Arminia Bielefeld.
Hannover hold the option to complete a permanent transfer move for Nawrocki, having agreed the clause as part of his season-long loan switch from Parkhead.
Udinese boss Kosta Runjaic, who managed Nawrocki at Legia Warsaw, reckons the defender will prove himself.
"Perhaps his move to Celtic came a bit too early for him," he said.
"But I trust him to make a big impression in the second division of German football.
"He is a very good guy, calm on the ball and he is very technically adept, he has a good passing game and is powerful in the air.
"I would assume he has matured a lot at Celtic in Scottish football.
"He can play in a back four or a back three.
"He has potential and I would expect Hannover to exercise their purchase option in a year."