KARL HEIN will never forget his Arsenal debut - for all the wrong reasons.

The Estonian keeper’s first half blunder allowed Brighton to equalize and then go on to take the wind out of Mikel Arteta’s high-flying side with a stunning comeback victory.

Hein, 20, was a shock inclusion in the starting line-up for the Premier League leaders as they looked to build on a three game winning streak in the Carabao Cup.

And the Emirates Stadium was bouncing when Eddie Nketiah fired Arsenal ahead in the 20th minute with a classy right foot finish from just inside the box.

A powerful run by Reiss Nelson split the Albion defence before a perfectly-weighted lay off fell for the striker to bend a shot past Jason Steele.

But the lead was short-lived and Hein was lucky to stay on the pitch after his unlucky slip as he raced off his line to meet Danny Welbeck’s run towards his goal.

Hein stumbled and in his recovery tugged the Brighton striker to the floor.

Welbeck turned in the penalty to equalise and from then on it was all revitalized Brighton as they rocked Arsenal with two second half goals to secure a thrilling win.

Hein was squarely beaten as Albion sub and Japan winger Kaoru Mitoma bent a shot beyond him on 58 minutes to claim his second goal in as many matches.

And full back Tariq Lamptey sealed a memorable night for The Seagulls with number three 19 minutes from time - his first goal for more than two years.

The deflating defeat is Arsenal’s first at home since April which was ironically a Premier League reverse against Brighton.

Arteta’s rejuvenated Arsenal had won 12 games on their own turf in a row prior to last night’s surprise setback.

Eager to maintain impressive runs of form, both bosses named relatively strong sides but with a hint of experimental flavor.

Arteta had keeper Turner on his bench even though the USA’s number one was named in his country’s squad for the World Cup prior to kick off, was not starting.

Turner has been injured recently suggesting he is not quite there yet in terms of fitness with the Group B game against England just 15 days’ away now.

Arsenal hit the post in the second half through Nketiah but Arteta had hoped to give some of his bigger stars a night off ahead of Saturday’s Premier League clash at Wolves - their last game before the World Cup.

But with the tie slipping away from him he was forced to bring on striker Gabriel Jesus in a bid to break down Brighton and stay in a competition that is much-criticized from the outside but which is hugely popular with fans.

With the 60,000 capacity Emirates Stadium rapidly emptying, Nelson managed a shot with three minutes left only for it to drift harmlessly wide.

Brighton manager Robert De Zerbi is now toasting a hat-trick of wins which now includes the current best team in the country and Champions League contenders Chelsea.