Are Cristiano Ronaldo's ex-teammates turning on him in the GOAT debate with Lionel Messi?

Euro 2024 might be Cristiano Ronaldo's last chance to win a major international trophy — and possibly the final opportunity to prevent himself from going down in history as the B-side to Lionel Messi.

Ronaldo or Messi; who is better? — has been a question that's become soccer's version of LeBron James or Michael Jordan for more than a decade, but the hypothetical battle has tilted significantly against the Portugal superstar over the past 18 months.

Messi's victory with Argentina in the 2022 World Cup, in the minds of many, struck the decisive blow in the argument, perhaps cementing the Argentina legend in the position of top dog for this generation.

The interesting thing about this clash of extraordinary talents is that it's not just one for the fans. Ronaldo cares about it, so does Messi, although the latter does a better job of hiding the fact.

And it is a conversation that has become entwined with their former teammates for a variety of reasons.

For years, there was an unwritten rule that if a player had played club soccer with Ronaldo, they would state his name whenever quizzed about who was the modern-day GOAT. 

If they'd played with Messi, you get the idea, they'd plump for him.

Germany legend Toni Kroos admitted as much in 2018, telling reporters: "We were not only teammates but also neighbors in the dressing room and neighbors in real life. Cristiano lived right by me.

"Seeing what a perfectionist he is was impressive. That is why it is forbidden for me to name Messi."

But then things began to shift. Ronaldo's reputation took a hit in 2022 when his second spell with Manchester United disintegrated into acrimony and poor performance, and ultimately ended with him announcing a move to Al-Nassr of the Saudi Pro League.

Weeks later, Messi finally lifted the Jules Rimet Trophy, scoring twice in an epic World Cup final against France and again in the penalty shootout.

Game, set, match, undisputed GOAT?

Perhaps so. When Kroos was quizzed at the end of that tournament, he had changed his tune.

"Messi deserves it," Kroos told Magenta TV, when asked the inevitable question about all-time greatness. "In terms of individual performances at championships, I've never seen a footballer play as consistently as this guy. 

"You have to remember that he has never played for clubs that I find appealing. That proves I mean it."

Then Wayne Rooney, who spent years alongside Ronaldo at United but was not necessarily the closest of friends with him, crossed the divide by also naming Messi.

"I have the greatest respect for Cristiano and when people argue he is the greatest, I know where they are coming from and respect that opinion," Rooney wrote, in London's Times newspaper. "But, for me, Messi is just different."

To be clear, the topic is still not universal.  There remain plenty of Ronaldo loyalists happy to make their voice heard, especially when he is criticized.

Former colleagues including French striker Louis Saha and Polish goalkeeper Tomasz Kuszczak, have been swift to come to Ronaldo's defense, and it is hard to find a Real Madrid player who doesn't rave about his time there.

However, heading into the Euros — which begin on Thursday with Germany v. Scotland (3 p.m. ET on FOX) — there is also an ultra-harsh school of thought among pundits that Portugal is better off when Ronaldo is on the bench.

Such beliefs surely stem more from what happened at the last World Cup than the Euros qualifying campaign, where Ronaldo was outstanding as Portugal became the only team to win each of its 10 qualification games.

Ronaldo and company begin their campaign against the Czech Republic on June 18, and will be favored to advance comfortably from Group F, which also features Turkey and Georgia.

FOX soccer expert Alexi Lalas believes Ronaldo's rivalry with Messi, who represents Argentina in the upcoming Copa América, still has some serious legs.

Ronaldo's only title with Portugal was the 2016 Euros, but he was forced into a spectator role after coming off injured early in the final.

"These great rivalries, like Borg-McEnroe, Magic-Bird, they are great duos that are not by design, they just evolve," Lalas told me. 

"Ronaldo and Messi push each other, they make each other better, and even in that grudging respect there is some resentment. They are so different, but they would admit they are better because of the prodding and pushing and pulling of wanting to be better than the other. 

"And, when you step back and look at it, as soccer fans we are all the beneficiaries of that, too."

Martin Rogers is a columnist for FOX Sports. Follow him on Twitter @MRogersFOX and subscribe to the daily newsletter.