The Wales manager, Ryan Giggs, has told Daniel James to “enjoy the challenge” and just be himself when he joins Manchester United later this summer. The 21-year-old Swansea winger is moving to United for £15m after the clubs agreed the transfer on Friday.

Giggs, talking before Wales’s Euro 2020 qualifer in Croatia on Saturday, praised James for the way he has coped with the death of his father, Kevan, last month as well as the upheaval of moving clubs.

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“I know the United fans will get behind him and enjoy watching him. It’s fantastic for everyone I think – for Dan, for Manchester United, and it’s a good deal for Swansea as well,” Giggs said. “It’s the biggest club in the world so my message to him is enjoy the challenge, don’t be anyone else, and you’ll be fine.”

James had a medical with United on Thursday to become Ole Gunnar Solskjær’s first summer signing. James broke off from preparations for Wales’s European qualifier in Osijek to head to United’s Carrington base.

Giggs said: “Dan is fine. He’s trained well and he’s a level-headed lad. Obviously after the terrible news with his dad we had to be flexible in everything that was on the table. He went home on Thursday, but he’s in a good place. He’s assured me he’s ready to play.

“You don’t want things weighing on players’ minds so if you can get it sorted, it’s better for us and the player as well. United are getting an exciting and fantastic player.”

James’s remarkable first full season in English season saw him go from a fringe player at a Championship side to joining United and being a key man for Wales. He scored the only goal in the defeat of Slovakia in Wales’ first Euro 2020 qualifier in March, but meetings with Croatia and Hungary in the space of four days will really test Wales.

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Temperatures for Saturday’s game with Croatia, who will be without the injured Ivan Rakitic, will touch 30C and the city’s Gradski Stadium is a dilapidated but intimidating venue with a capacity of just under 19,000.

Giggs said: “I was talking to Chris Mepham about my experiences as a player. The first time I went to Galatasaray away we were welcomed at the airport with a sign which said ‘Welcome to hell’. There were 5,000 people there. Of course the home team are going to try and make it as difficult as possible for you. That’s what we try and do.

“Croatia have got to the World Cup final and shown they’re a great team, but we’ve got a team that got to the Euro semi-finals and we have really good competition for places. We’re missing a top player in Aaron Ramsey and you have to be wary of the opposition’s strengths. Croatia have good players like Luka Modric, but you can’t just focus on one individual.”

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Joe Allen – winning his 50th cap – will be key if Wales are to keep possession, while Tottenham’s Ben Davies is poised to start after surgery to a hernia problem was delayed.

Giggs is likely to deploy Gareth Bale as a lone striker. Bale, whose future at Real Madrid remains uncertain, spent the first part of a training session on Friday working alone but is fit to start.

“He’s been excellent in training and he’s ready like he always is to play for his country,” Giggs said. “There has been a lot of speculation around him but when he comes away with us he forgets all that because he’s with his mates.”

Modric also believes Giggs will brush off his Madrid misery here. “I know what playing for the national team means to Gareth so I don’t think his Real form will affect him,” he said. “I expect him to be at his best.”

Croatia’s manager, Zlatko Dalic, said Uefa had insisted on a 3pm kick-off and expressed anger at having to play in the heat of the day. “Croatia is second in the world and they should have shown us more respect,” he said.