Fabian Schär has been declared fit by United's medical team despite being knocked unconscious in Switzerland's Euro 2020 qualifier but will sit out the trip to face the Gunners as the defender serves the final game of his two-match suspension.
Jamaal Lascelles has returned from a knee injury, which saw the Newcastle captain miss the Magpies' 2-2 draw at Bournemouth a fortnight ago, and Benítez feels a trio of returning players from their respective national sides should be ready before the clash at the Emirates Stadium.
Benítez said: "The international break is always quite complicated, particularly at this stage of the season, because you can see a lot of injuries. The players are tired and a lot of the national teams are playing for something so they are pushing players.
"We have some knocks but Sean Longstaff is the only player who is injured for us at the moment. Schär has had another test this morning and he was fine, training with the team.
"Today, we have had (Christian) Atsu, (DeAndre) Yedlin and (Miguel) Almirón coming back from international duty. We will need to make sure that they are fine tomorrow. When a player returns on a Thursday evening, it is quite difficult to get them ready for a game on a Saturday. But this game we play on Monday, so we have time.”
Newcastle remain closer to a top-ten finish rather than the fears of relegation, with United six points adrift of tenth place Leicester City and seven ahead of Cardiff, who occupy the final spot in the bottom three.
With Arsenal sitting in fourth place and in the pursuit of Champions League qualification, Benítez expects a strong test against Unai Emery's side but is hopeful of his side replicating recent league performances in order to move upwards in the top flight.
"Monday night will be a tough game," he added. "Arsenal are doing really well and they are normally a team that likes to keep the ball and they have the quality to do it, but we know exactly what we have to do.
"We still have to win more games but it depends on the other teams. We just need to carry on - the next game is the most important and is like a final for us.
"Sometimes you need a bit of luck, but we can compete against anyone. The team is quite solid and we have confidence in ourselves. We are doing a lot of things with more confidence – we are creating more chances and we have more of a threat in attack. The players know exactly what we are trying to do.
"We have showed a lot of character. We were fighting until the end against Everton, which was a difficult game against a very good team. It was a boost for everyone in terms of the confidence for the next games.
"I think it was different when we played Bournemouth because we deserved more during the game but we were lucky enough to get the second goal. There was a feeling that we can fight because we are now in a position that we can get points against anybody."
