Manchester United rising star Aaron Wan-Bissaka says it was an eye-opener when he first faced Wilfried Zaha in training – as the pair prepare to do battle in the Premier League.
Former Crystal Palace team-mates Wan-Bissaka and Zaha are set to be on rival sides on Thursday when United travel to Selhurst Park.
And that means full-back Wan-Bissaka will be charged with stopping the Palace winger's mazy runs, which as he once discovered on the practice pitch is no easy task.
Wan-Bissaka was converted from a striker to a defender while a youngster with Palace, a gradual process that included a spell on the wing.
"Then it started from a training session when someone had to fill in at right-back," Wan-Bissaka told United's official website.
"Training against Wilf, I think he sort of prepared me for what it is like playing in the Premier League.
"I learned a lot from him. He's an unpredictable player and tests like that are ones that made me a better player."
Zaha has terrified defences in Palace colours, but a stint at United did not work out earlier in his career and he soon rejoined the Eagles.
For Wan-Bissaka, the long-term prospects look bright with Ole Gunnar Solskjaer's team, but the 22-year-old will always look back fondly on his time with Palace, who stunned United 2-1 at Old Trafford earlier in the season.
He predicted it would feel strange to return to Selhurst Park, particularly given a near-empty stadium awaited, but added: "Palace mean a lot to me.
"They are the team that brought me through the system and, without them, I don't think I'd be here. They've given me chances to show what I am capable of doing."