Barcelona defender Thomas Vermaelen revealed just how intense the club's training methods are ahead of his return to Arsenal.
Vermaelen and his Barca team-mates travel to Arsenal for the first leg of their round of 16 Champions League tie on Tuesday, and the defender provided an insight into the European champions' practice sessions.
"The first thing I noticed here was the intensity of the pressing," Vermaelen told the Telegraph.
"The pressure is on straight away when we lose the ball. We do a lot of positioning games, focusing on getting the ball back. The pressure the players put on you is incredible, you have no time on the ball."
The Belgian spoke about how Barcelona regularly work on a piggy-in-the-middle game known as a 'rondo'.
He said: "We always do it at the start of training, it doesn't only warm you up but it's a training session in itself, you try to keep the ball in possession and make the guys in the middle do the pressing.
"We did it sometimes at Arsenal but not a lot of clubs do it like we do it here.
"It's a tradition. Even if we have a game in the evening, we come here in the morning and do a rondo."
Vermaelen added that he has "warm memories" of Arsenal, where he made over 100 appearances between 2009 and 2014.
"I watch a lot of Arsenal games because I have warm memories of the club, and because they are a very attractive team," he said.
"I watched the Leicester game last week, it was very stressful but these are the most beautiful games to win.
"Now the title race is wide open, if they hadn't won it would have been more difficult but now it's on. I always said at the start that Arsenal had a big chance to win it.
"Unfortunately we had to go our separate ways but luckily I signed for a beautiful club like Barcelona."