Rivalries can run deep - particularly when a World Cup is at stake.
But despite being on opposing sides as they battled it out for a place in the semi-finals, there is still clearly a great deal of respect between Luka Modric and Casemiro.
The former Real Madrid team-mates came up against each other in the midfield contest between Croatia and Brazil in Friday's World Cup quarter-final meeting in Education City Stadium, Doha. And while the game was tightly poised on a knife edge, the pair still found time to swap shirts at the half-time break.
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Normally saved until the end of the match, Modric and Casemiro left the field topless, clutching the other's shirt. It was Casemiro who had suggested the swap as he shouted to Croatia's captain whilst walking slightly behind him as they walked off the pitch.
The score was tied at 0-0 at the time after Croatia had arguably had the better half. Modric and Casemiro have a strong relationship from their days together at Madrid, where they spent almost a decade in midfield together, winning five Champions League winners' medals in the process.
Casemiro opted to call time on his career at the Bernabeu in the summer to complete a switch to Manchester United, while Modric continues to flourish in Madrid, despite being well into the twilight of his career aged 37.
It was only the second time the two players had come up against each other on the international stage, a friendly back in 2018. Speaking ahead of the match, Madrid star Vinicius Jr. said: "Playing against Modric is going to be very special.
"As far as neutralising him goes, I'll leave that to Casemiro because he can do a better job than me! He knows Modric really well because they played together for a long time."
Modric and Casemiro formed a stunning partnership in Madrid's midfield, alongside Toni Kroos, but neither could gain the upper hand during Friday's tie. The game ended goalless after 90 minutes with Modric failing to find the spark to dent Brazil's hopes, while the tournament favourites missed several chances to put the game to bed.
Some fans were angered by their gesture to each other at half-time with the game far from over. One fan wrote on Twitter : "Casemiro and Modric swapping shirts at half-time. Red card offence."
Another joked: "Someone get Roy Keane on the BBC coverage quickly, Modric and Casemiro have swapped shirts at half time."
Others were less offended by the exchange, with one fan writing: "When you’ve won five Champions League medals together, you can do whatever you want."
Casemiro has previously joked Modric and Kross would be his two ideal midfield partners in the Brazil side were they eligible to play. He and Modric shared a playful joke prior to swapping shirts where Casemiro gave his old team-mate a playful slap round the face after he had helped him to his feet.
