Xulu had an amazing season with United whom he joined after a two-year dry spell at Kaizer Chiefs where he was hardly ever used.
Maritzburg have already lost captain Bevan Fransman who refused a contract renewal.
The club have however moved quickly to replace him by signing Denwin Farmer from SuperSport United.
“Xulu is one of the players City are looking at. He is very experienced and is seen as a capable replacement for Robyn Johannes who has left for Wits,” said a source.