Schalke midfielder Bentaleb, who completed his move to St James' Park earlier this week, and Inter Milan winger Lazaro, who was undergoing a medical on Tyneside on Friday morning, are both expected to be involved.
However, defenders Emil Krafth (ankle ligaments) and Florian Lejeune (groin) are out after being injured in Tuesday's 2-2 draw at Everton. Paul Dummett has undergone surgery on his hamstring and will not play again this season.
Striker Allan Saint-Maximin is available after being rested for the trip to Goodison Park, but defenders Javier Manquillo (hamstring), DeAndre Yedlin (knee) and Jetro Willems (knee ligaments), midfielder Ki Sung-yueng (knock) and frontmen Andy Carroll (hip) Dwight Gayle (hamstring) and Yoshinori Muto are all missing.
Oxford are set to be without a number of players for their trip to St James' Park.
Midfielder Cameron Brannagan (knee) continues to be sidelined while the cup tie will come too soon for winger Anthony Forde (ribs).