Sokratis replaced the injured Laurent Koscielny in the second half and scored with his fifth touch
Arsenal powered into the last 16 of the Europa League with a comfortable second-leg victory over Bate Borisov at Emirates Stadium.
Trailing 1-0 from the first leg, they scored inside four minutes when Pierre-Emerick Aubameyang's cross was turned in by Bate defender Zakhar Volkov.
Centre-back Shkodran Mustafi made it 2-0 before the break with a powerful header following Granit Xhaka's corner.
Substitute Sokratis Papastathopoulos headed in the third goal after an hour.
Bate were denied an equaliser just four minutes after Arsenal had taken the lead, when Stephan Lichtsteiner slid in to make a goalline clearance from Stanislav Dragun's header.
The visitors also went close when Maksim Skavysh hit the side-netting in the first half, but Arsenal had better chances through Alex Iwobi, Xhaka and Aubameyang.
Arsenal boss Unai Emery had vowed his side's performance was "going to be different" from their lacklustre display in Belarus and he was not wrong.
The Gunners looked full of energy in the opening stages - winning two early corners and forcing a save from keeper Denis Scherbitski when Iwobi pounced on Lichtsteiner's cross.
They were rewarded when the ball bounced off Volkov's shin and into the back of the net to give them a crucial equalising goal in the tie.
Arsenal continued to press high up the pitch and created chances in both halves. They had 22 shots - including 15 in the box - and put in 24 crosses from open play.
Xhaka forced Scherbitski into a smart save with a powerful long-range effort in the first half, while Mesut Ozil - making just his second start of 2019 and first in four games - poked a shot wide of the left post and Aubameyang's free-kick was saved after the break.
Bate did come close on a few occasions - Skavysh got in behind Nacho Monreal only to slam the ball into the side-netting, before Dragun's header was kept out by Lichtsteiner.
But Arsenal were dominant throughout and never really looked like conceding a costly away goal.
The Gunners have not made the final of a European competition since their Champions League defeat by Barcelona in 2006, and were knocked out in the semi-finals of this competition last season.
They will hope to go one step further this time around though - the prospect of securing an automatic spot in the Champions League by winning the Europa League is a strong motivator.
Arsenal manager Unai Emery speaking to BT Sport: "We wanted this result but also we wanted to play for our supporters here, to improve and build our mentality after the first match away, which was not good. We did our best to come back [in the tie] and the team worked very well.
"But we also had to take precaution because if they scored they can be back in the match. Our message was if we score, carry on. If we scored two, carry on. Carry on and carry on. We needed two, three or four goals for more precaution in the 90 minutes.
"The players did our game plan as we wanted and they arrived in the box a lot with a lot of crosses. And we showed the efficiency we went, which we didn't have away."
Alexander Hleb of Bate Borisov comes on as a substitute on his return to Arsenal during the UEFA Europa League Round of 32
POSSESION / SHOTS / CORNERS
ARSENAL 68% -22 -10
BATE 32% -4 - 0
