The right-back returned from international duty with some hamstring discomfort on his England Under-21 debut in Albania last week.
Moyes decided against risking Johnson in Sunday’s 2-1 win over Everton, leaving the 22-year-old completely out of the matchday squad.
It’s not believed to be too serious an injury but while Moyes is hopeful the full-back can feature in the first leg of West Ham’s historic Europa League quarter-final against Lyon, his exact status remains unclear.
Ryan Fredericks started in place of Johnson against Everton and, despite performing well at times, he can be a liability at the back. West Ham have at least been given a boost by the return of Vladimir Coufal after a hernia operation.
The Czech international was named on the bench on Sunday but didn’t get a chance to feature ahead of Lyon, which could be a concern if Johnson isn’t fit to return.
The same cannot be said for Jarrod Bowen, who played 70 minutes on his return from an ankle injury and secured the winner against Frank Lampard’s ailing Everton.
“That’s what you want when you’re out,” Bowen said. “It’s been annoying with the timing, but injuries happen on your journey and to get back into the starting XI and get the goal and three points, you can’t ask for much more.
“Obviously I won’t be where I was before the injury, but it’s about building that game by game and having confidence in myself. I’m happy to score and get the win.”