The Denmark international has been largely disappointing for Roma since signing for the Serie A giants in the summer on a season-long loan.
Kjaer was at fault in Roma's 4-2 defeat at Cagliari on Wednesday, and Sabatini has admitted that the club may not exercise their option to buy the 22-year-old at the end of the campaign.
"He has been a bit unlucky," Sabatini told Gazzetta dello Sport. "We will have to make a big sacrifice to sign him.
"As such, we will wait and see."
The 22-year-old defender was loaned out to Roma after enduring a disappointing first season at Wolfsburg following a transfer from Palermo.
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