Javier Mascherano talks about the moment his life at Barcelona changed. One tackle, against Arsenal, sent the Argentinian’s career trajectory in a different direction and turned him into a centre-back. If Arsene Wenger is to take his team into the quarterfinals of the Champions League, the Arsenal manager needs to find a way to spin Mascherano’s life on its head once more.

The tackle was on Nicklas Bendtner in the second leg of the 2011 semifinal. With time running out at the Camp Nou and Barca ahead 4-3 on aggregate, the Arsenal forward was clean through on goal and had the chance to send his side into the final. Mascherano slid in and whipped the ball away. He told The Guardian: “That tackle marked a before and after.”

The out-of-place midfielder was transformed into a stopgap defender. It was a way of getting him into the team. Even a player of the Argentinian’s quality was never going to displace Sergio Busquets in Barca’s system.

Five years on, Mascherano is still in the same role. It is not ideal for club or player. Finding a way to exploit his weaknesses in this position is easier said than done but Arsenal have the tools to expose the converted midfielder.

The London club have an abundance of pace. If they can get Theo Walcott running down the inside right channel, it will give Barca’s makeshift centre-back problems. Mascherano’s great strength has always been his terrier-like appetite for the ball, but the downside of this is a tendency to get sucked into midfield. This can place pressure on Gerard Pique. If Mesut Ozil can get on the ball and exploit the space behind the Argentinian, Arsenal will get chances.

Mascherano is short for a central defender. If Wenger opts to play Olivier Giroud, the Arsenal forward will have a significant height advantage if he can isolate the smaller man in the area. Early balls from Alexis Sanchez and the home side’s full backs will ask questions of the Barcelona defence.

The problem for Arsenal will be keeping their opponents out. The attacking triumvirate of Lionel Messi, Luis Suarez and Neymar would give any back four a headache. It is vital that Wenger’s side play with discipline. Often, the Arsenal full backs charge forward together, leaving Per Mertesacker and Laurent Koscielny isolated. They need to play with more restraint out wide.

The Catalan side like to pass the ball around deep in their own half to draw a press. Once the opposition push into Barca territory, it opens up space behind them. Barcelona can zip the ball forward at pace to give their forwards running room. Arsenal need to stay compact and refuse the bait. When the home team get the ball, they need to get it upfield quickly.

There has been a shift in recent months in the way sides in La Liga approach matches against the Spanish champions. Fewer teams have “parked the bus” and tried to keep Barcelona from scoring. Domestic opponents have tried to be more open and attack. It has not worked: Barca are on a 32-game unbeaten run and have won their past eight league games, but the shift in tactics is underpinned by a belief that, as good as they are, Luis Enrique’s side can be got at. Arsenal have more quality and pace than most La Liga teams and may enjoy more success.

Wenger’s side have been written off by many, but Barcelona are not unbeatable. It is hard to see this first leg being tight and cautious. The Champions League holders do not play that way. Yet an open game could suit Arsenal. As long as they are not blown away in the first leg, they will get the opportunity to score at the Camp Nou in the second leg.

Five years ago, against an arguably more rounded Barcelona side — though without the brilliant front line of today’s team — Arsenal came within a last-ditch tackle of reaching the final. Now they have a chance to advance if they get their approach right at the Emirates. It will take discipline, pace and a healthy dose of good fortune but it is foolish to write off Wenger’s team.

The Frenchman knows how big the task is to beat Barcelona. “They are not perfect, but not far off it,” he said. Up front, perhaps, but Mascherano’s continued presence in the back four suggests perfection is still a fair distance from Barca’s defence.

Nonsense about the FA Cup
The usual FA Cup hand-wringing is taking place after the fifth round’s proximity to the Champions League caused Manchester City to put out an unrecognizable team for their tie against Chelsea. Sure enough, City got walloped 5-1 and the cries of “the big clubs don’t care about the FA Cup” went up.

OK. How does that one work? In the past 20 years, Arsenal, Chelsea, Manchester United and Liverpool have won the trophy 17 times between them. City won it once too.

The only teams outside these to lift the trophy are Portsmouth and Wigan Athletic. Imagine what a closed shop it would be if the so-called big clubs started caring again?