Arsenal legend Martin Keown believes it was just a lack of experience that cost his former side in a shock 1-0 defeat to Porto in the Champions League on Wednesday night.

The first leg of the last 16 tie was played in Portugal and there was little between the sides on a night of few chances. However, deep into injury time at the end of the game, Galeno curled in a superb long-range effort into the corner of the goal, past a diving David Raya.

It was an immense finish, but it came from a misplaced long pass from Gabriel Martinelli and Keown felt that was a sign of the inexperience in the Gunners team.

Mikel Arteta’s young side has precious little experience in the knockout stages of the Champions League and that showed as they failed to have a shot on target and then conceded at the death.

‘It was a sucker punch really,’ Keown said on TNT Sports. ‘Professional performance, defended well, could have created more opportunities but then you give the ball away cheaply and Galeno scores a wonderful goal.

‘You can’t help think that maybe experience has cost Arsenal there a little bit, it’s the competition of late goals and it’s a young team that’s learning in Europe and I hope it doesn’t come back to haunt them.’

He added: ‘Neither team were really creating that many opportunities, it got a bit loose at the end. I just think that it’s inexperience.

‘Martinelli there could have kept possession. you see the game out. Jorginho came on to do that very thing so that will be quite sickening for this young team to concede in the way they did.’

The second leg will be held in north London on 12 March with a place in the quarter-finals on the line.