Wales will be without injured trio Ethan Ampadu, Sam Vokes and Tom Lawrence for their opening Euro 2020 qualifier against Slovakia in Cardiff on Sunday.
Arsenal midfielder Aaron Ramsey will miss Wednesday's friendly against Trinidad and Tobago in Wrexham.
But manager Ryan Giggs confirmed Ramsey will be available to face Slovakia.
David Brooks, Daniel James and James Lawrence should be fit despite training separately from the main squad.
Wales have been training at Manchester United's Carrington base. Although Ramsey was not taking part in Tuesday's session, he was at the ground for treatment.
"Aaron's just got a slight knock to his thigh, so we're just monitoring that. He should be OK for the weekend. He won't be involved tomorrow," Giggs said.
"They [Ampadu, Lawrence and Vokes] have got different injuries. Ethan's got a slight back strain.
"Tom Lawrence, I was at the game, took a blow to his other ankle. He was struggling with one ankle, then got a knock on the other ankle.
"And Vokesy's been struggling with his groin, came back on the weekend, played 70 minutes and just felt it again. So the three of them are unavailable."
'Ampadu like Steven Gerrard'
While Ampadu has established himself with Wales this season, the 18-year-old defensive midfielder or centre-back has endured a frustrating campaign with his club Chelsea.
He has made only three Europa League and two FA Cup appearances this term, with his playing time limited by injury.
With the former Exeter City player still suffering from growing pains in his teens, Giggs compared him to former Liverpool and England midfielder Steven Gerrard, who suffered from similar issues early in his career.
"He reminds me of Steven Gerrard because he's still growing," Giggs added.
"Every time we meet up I think he's grown, or I've shrunk - one of the two!
"He's growing out, he's growing up but he's at that stage when he's growing and in between playing and not playing. I think that's the main issue.
"Steven Gerrard had it and a couple of players had it when they're still growing and they pick up these little knocks and strains.
"I can see [Chelsea manager Maurizio] Sarri wants him around the first team.
"But it's just been a bit stop-start, together with the injuries, which is frustrating because he is an amazing talent and he's shown that in the games he's played."