Bale comes up against his Real team-mate and great friend Modric in Osijek on Saturday having suffered a nightmare end to the season at the Bernabeu.
The Welshman was dropped from the starting XI, and boss Zinedine Zidane even refused to bring him off the bench in the final La Liga game when Los Blancos were losing 2-0 at home to Real Betis.
Real are reportedly keen to get Bale off the wage bill this summer and have already signed Serbia striker Luka Jovic from Eintracht Frankfurt for £52.4million, while also being close to completing a club-record £130m move for Chelsea’s Eden Hazard.
“It’s very different to play for your club or in international football,” said Modric, who revealed he had not spoken to Bale ahead of the Group E qualifier at the Stadion Gradski vrt.
“There’s no correlation in form between those two.
“I know what playing for the Welsh national team means to Gareth, so I don’t think his lack of minutes for Real Madrid will influence his performance.
“I expect him in top shape. We have to stop him as well as we can, we have to limit the great talent he has.”
World Cup finalists Croatia started their Euro 2020 qualifying programme with a 2-1 home victory over Azerbaijan in March.
But they were stunned by Hungary three days later, losing 2-1 in Budapest, as Wales opened their campaign with a 1-0 home win over Slovakia.
“After Hungary, we have no space for other bad results,” Modric said.
“We expect a very tough match against an opponent I think, along with Croatia, is the best in the group.
“Wales is a very good, organised team. Gareth is obviously their best player but they have a lot of good players, especially going forward.”
The searing heat in Osijek has been an area of concern with the game set to kick-off at 3pm local time.
Wales manager Ryan Giggs spoke about the importance of giving players “the right information on hydrating” for the game, with the temperature at kick-off expected to touch 30 degrees.
Giggs’ players could even have ice baths before the game and also at half-time to help them cope with the heat.
Croatia coach Zlatko Dalic was critical of the decision to stage the game in the afternoon and accused UEFA of disrespecting his side.
“It’s going to be hot,” Dalic said. “I don’t know who made the decision – UEFA did.
“Croatia is second in the world and they should have shown us more respect. It’s going to be difficult for the players but it’s the same for both teams.”
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