No fewer than four defenders might have cut out Wilshere's deep ball but, if Scherbitksi blocked Walcott's first header, he succeeded only in teeing the ball up for Walcott to stab elegantly home.
Arsenal face a tricky away tie against BATE Borisov in Belarus in the UEFA Europa League and their already tricky predicament has been toughened by the unavailability of several first-team players. With Reiss Nelson, Joe Willock, Josh Dasilva, Charlie Gilmour, Vlad Dragomir and Marcus McGuane also travelling for the fixture.
Nearly immediately after that in the ninth minute, Wilshere played a one-two with Giroud to beat three defenders and then square a cross towards Walcott, who after watching Denis Scherbitski save his header, routinely finished the rebound.
Olivier Giroud of Arsenal celebrates after scoring his team's fourth goal during the Premier League match between Arsenal and Leicester City at the Emirates Stadium on August 11, 2017 in London, England.
Arsenal were in complete control, and the only surprise was that it took the Gunners until the 22nd minute to extend their lead - and it was a gift.
"He is on a good way back to his best and he showed that tonight".
The Frenchman slotted calmly from the penalty spot after Stanislaw Drahun was deemed to have pulled back Shkodran Mustafi.
The visitors were suddenly wracked by anxiety, and the hosts could have made it 4-3 when Aleksandr Volodko's side-foot effort from a cut-back skewed inches wide of the target.
Holding's attempted tackle in the penalty area rebounded up, Mertesacker stumbled and Mikhail Gordeichuk slammed the ball into the roof of the net.