Sunderland have signed defender Ondrej Celustka on loan from Turkish Super Lig side Trabzonspor on a season-long loan.
The 24-year-old has made 55 league appearances for his parent club, following spells at FC Tescoma Zlin, Slavia Prague and Palermo.
"Signing so many players from abroad with no Premier League experience is risky.
"If they can adjust to the rigours of the English winter then Sunderland could enjoy a successful season.
"The manager's temperament will be under the spotlight but there's no doubt this season will be an adventure."
BBC Newcastle's Nick Barnes
Celustka, who is principally a right-back, played 18 games for the Czech Republic Under-21 side but is yet to win full international honours.
He becomes the 10th new arrival on Wearside this summer.
Manager Paolo Di Canio had already added to the defensive ranks, bringing in Valentin Roberge and Modibo Diakite, while goalkeeper Vito Mannone, midfielders Cabral, Emanuele Giaccherini, David Moberg Karlsson and El-Hadji Ba, plus strikers Duncan Watmore and Jozy Altidore are the other new arrivals.
Right-back has been a problem position for Di Canio, with midfielder Craig Gardner filling the role during pre-season fixtures against Tottenham, Manchester City and FC Midtjylland.
However, Gardner is suspended for the opening match of the season, at home to Fulham on Saturday, while natural full-back Phil Bardsley has not featured for the Black Cats this summer.