Best friends off the pitch - but fierce rivals on it.
It's the classic footballing dilemma.
And for former Tottenham and Everton star Aaron Lennon, there was one Chelsea pal in particular who always sparked some great contests on the field.
The winger made over 400 appearances in the Premier League, coming up against some of the toughest defenders in the top flight during a professional career which spanned almost two decades.
But one player stood out for him for the sheer challenge he posed on the pitch in their many meetings.
When asked to name the one player who he ranked as his toughest opponent, Lennon told talkSPORT it was actually a former international teammate.
"All round, I'd probably say Ashley Cole," he admitted. "We had some amazing battles.
"We played for England together, so it was quite funny. I've said this a few times, we were quite good friends off the pitch, but when we played against each other, he wouldn't speak to me at all.
"So we'd get to the tunnel and I'd be like, you all right, Ash? Looking forward to today, mate. And he'd literally just blank me.
"And then like I said, soon after the game, he'd be coming up joking, but throughout the game, he wouldn't speak to me. And I'd be trying to get in his head a little bit. But it was a good banter.
"But like I said, Ashley Cole was amazing. Amazing player for a club and country. Top, top player. And a great lad."
Cole spent eight years as a Chelsea player, before eventually signing for Roma in 2014.
But before he did, he came up against England teammate Lennon many times as the two contested a number of London derbies.
"I think one of the games we played on Saturday," he recalled. "And we were meeting up on a Sunday and he was so angry with me. But then the Sunday, we were literally best friends again.
"But the whole Saturday, he didn't speak to me. Even after the game, he didn't want to talk to me.
"I think we (Spurs) won that game. So no wonder he didn't want to speak to me!"
Chelsea and Tottenham faced each other 20 times during the period that Cole and Lennon were both at the clubs between 2006 and 2014.
Of those fixtures, Chelsea won eight of those, Spurs won four and the remaining eight games ended in a draw.
But it is clear that the two pals both gave each other their equal share of trouble on the pitch.
Back in May, Cole actually admitted to Goal that Lennon also featured highly on his own list of toughest opponents.
“I played against some top top players, you know," he said. "Aaron Lennon always gave me a tough time, Theo Walcott, Raheem Sterling, but the main one I would have to say is Cristiano."
And Cole was not the only player who rated Lennon as a seriously tough opponent to face.
In fact, former England defender Wayne Bridge previously told talkSPORT that he ranked Lennon as one of the two toughest opponents he had ever faced during his career.
And Lennon was flattered by the nod, admitting that the ex Chelsea and Man City star had always given him an excellent contest.
"Yeah, I'll take that!" said Lennon. "I had a good relationship with Bridge, to be fair, because I played with him for England also. Really good lad, got on with him really well.
"Like I said, I did have some good battles with him on the pitch. So yeah, that's nice to hear. And like I said, Bridge was a top player also.
"He probably didn't give himself enough credit, but Bridgie was a top, top full-back. So he was hard to play against also for me. So yeah, it's nice to hear."