Celtic captain Callum McGregor and Rangers midfielder Ryan Jack are rivals most of the time that they share the pitch together.
Both have been involved in battles across the park in many derbies and have fought for leagues and cups across various seasons.
However, they have also featured together for Scotland at international level.
In the current squad selected for the fixtures against Cyprus and Spain, McGregor and Jack are two of only three players who ply their trade north of the border.
And the Ibrox midfielder has opened on why he enjoys playing with the 29-year-old.
He told Sky Sports: "We have a great relationship through the number of games that Callum and I have played.
"I obviously don't know what the manager is going to go with, I don't know what the formation or the personnel is until we obviously meet up.
"There are five or six midfielders in the squad. You look at it and think that anyone could play, anyone could step in."
READ MORE: Oh Hyeon-gyu's big Celtic moment made Scottish football take notice
Meanwhile, Celtic defender Anthony Ralston has been drafted into the latest Scotland squad.
As expected, Dominic Hyam has also joined up with Steve Clarke's side.
The Blackburn Rovers centre-back earns his first international call-up aged 27.
The defender represented Scotland at youth level but has never been considered for a senior call-up until now.
His impressive form with Rovers as they look to earn promotion to the Premier League via the Championship play-offs has caught the eye of Clarke.
Ralston, who has struggled for game time at Celtic this season, has also been called in for the games against Cyprus and Spain.
The pair have been brought in for cover after Jack Hendry was forced to withdraw through injury.
While Hyam is called up to his first Scotland squad, Ralston has been a regular feature in the national team setup over the last 18 months.
His transformation at Celtic Park under the guidance of Ange Postecoglou led to his international recognition from Clarke.
Our Celtic Digest newsletter brings exclusive content directly to you rather than solely through the website. You can already find us on YouTube, Twitter, Facebook, TikTok and Instagram but we will also send bespoke opinion pieces and special features directly to your email inbox every evening. Not only will you receive this article from Sean Martin, Tony Haggerty or Aidan Macdonald (or, sometimes, from all three) but you will also get easy access to our best content from the last 24 hours too. It’s a great way to keep up to date with what’s happening at Ange Postecoglou’s Scottish champions. To sign up, simply take five seconds to type in your email here. Simple!
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here