Miguel Almiron has returned from international duty with a knock.
The Newcastle United midfielder was sent off for Paraguay seven minutes after coming off the bench against Mexico during the international break.
Almiron was dismissed for a lunge at Jose Juan Vazquez in the game, which Mexico won 4-2.
The 25-year-old returned to Tyneside this week with a knock ahead of Monday night's Premier League game against Arsenal at the Emirates Stadium.
Christian Atsu and DeAndre Yedlin also have minor problems.
“I can say we have knocks, little things,” said Rafa Benitez. “(Sean) Longstaff is the only one with an injury. Schar has had a test, and he’s fine.
“I think the knocks will be fine. Atsu, Yedlin, Almiron ... we think they’ll be fine, but we will check.
“Everyone has been training apart from Longstaff.”
Newcastle's form has improved since the January arrival of Almiron from Atlanta United in a deal which could cost the club £21million.
Jamaal Lascelles is available after missing the Bournemouth game because of injury.