Cruzeiro midfielder Everton Ribeiro has told ESPN Brasil that he would fit into the Manchester United side.
Portsmouth have named Richie Barker as their new manager and Steve Coppell as director of football.
The defender becomes Mick McCarthy's first signing of the January transfer window and will remain at Portman Road until January 29.
Kisnorbo has been given clearance by his parent club to feature in Town's FA Cup third-round tie at Aston Villa on Saturday.
The 31-year-old Australian moved to Britain when he joined Hearts in 2003 but switched south of the border to join Leicester two years later.
After four years with the Foxes he linked up with Leeds, where he has made a total of 58 appearances although only one of those has come this season, a Capital One Cup outing in August.