Eustace will provide useful cover while George Boateng, Mark Wilson and Juninho recover from injury and he could earn himself a permanent deal if he impresses.
The 23-year-old was dogged with injury last season but has made over 20 starts for the Sky Blues this season. He was omitted from Coventry's squad last night for their FA Cup replay against Cardiff in arder that he did not pick up an injury that could affect the deal.
There are also reports that Steve McClaren is negotiating with Tottenham to bring Les Ferdinand to the Riverside on a short term contract until the end of the season.
The 36-year-old hasn't featured for Glen Hoddle's side this season, but he still remains the Premierships 3rd top scorer of all time, behind Alan Shearer and Andy Cole.