Alan Pardew admitted Yohan Cabaye's future needs to be sorted out after seeing Newcastle draw a blank against West Ham.
Cabaye was a notable absentee as Newcastle were forced to settle for a goalless draw against West Ham at St James' Park on Saturday.
Arsenal have failed with one bid for the France international, and one newspaper report on Sunday claimed he is refusing to play.
Arsene Wenger on Saturday said Cabaye's absence from the Newcastle side was not down to any second offer from Arsenal, and Pardew still hopes to keep the player.
But the United manager wants the issue sorted out quickly either way.
"The Cabaye situation needs to resolve itself one way or the other because if we lose him we need to replace him," Pardew told Sky Sports.
Despite being held by West Ham, Pardew was happy with the performance of his players after they responded to Monday's 4-0 defeat by Manchester City with a clean sheet and a first point of the season.
"We had to dig in after Manchester City and really show our resilience which we did today," added Pardew.
"Defensively we did not put in a bad performance, offensively we know we have to improve, but we had some key players missing today and hopefully when we play Fulham one or two will be back."