Town have taken defenders Rui Marques and Edwin Ouon on a three-day trial. Marques left Portuguese side Maritimo at the end of last season and Ouon has been released by Belgian club Royal Antwerp.
One or both could play in Tuesday's first home friendly of the pre-season programme against Rangers and may be invited to go on the two-match tour of Hungary.
Boss Joe Royle told the club site: "The two lads will be with us over the next three days and will train with the first team.
"They have been recommended to us and we will have a look at them. They are both available on a Bosman."
Marques, 27, was born in the Angolan capital Luanda and started his career with Benfica. He has also played in Germany with FC Baden, SSV Ulm 1846, Hertha Berlin and VfB Stuttgart. Primarily a full-back, the Angolan international has also played at centre-half.
Frenchman Ouon is mainly a central defender and played with Metz, Red Star de Paris and Italian side Cagliari prior to joining Royal Antwerp in 2002.
Ouon failed a drug test in March 2003, testing positive for an anabolic steroid, however a second test proved negative and he escaped a two-year ban.
Both players have had trials elsewhere in England, Marques at Leeds and Ouon at Watford. Last summer the Frenchman spent time with Leicester but failed to win a contract.