Arsenal were dealt a significant injury blow in midweek when it was confirmed that Kai Havertz, their de facto centre-forward, will miss the rest of the season after damaging his hamstring.
He joins Gabriel Jesus and Bukayo Sako in the treatment room, meaning Mikel Arteta had to deploy out-of-form Raheem Sterling and 17-year-old Ethan Nwaneri either side of makeshift focal point Leandro Trossard.
Throughout the first 45 minutes, the Gunners’ lack of attacking firepower was clear for all to see. Besides a Declan Rice header that trickled wide of the post, they created next to nothing, meaning Mads Hermansen had a quieter afternoon than he might have expected between the sticks.
Leicester, meanwhile, were hardly dangerous, but Wilfried Ndidi did force David Raya into a save from the edge of the box, and on the brink of half-time, the Nigeria international headed wide when unmarked with the best chance of the opening period.
It was much the same initially after the break, but as the game approached the hour mark, the intensity from both sides increased.
Nwaneri was his side’s greatest threat, and he almost broke the deadlock with a delightful strike from just outside the area that grazed the crossbar.
In response, Bobby De Cordova-Reid tested Raya with a fierce strike, although it was a comfortable save for the Spaniard given it was straight at him.
Nwaneri later struck the post with even more venom as it appeared that any visiting breakthrough would involve the teenager.
That ultimately proved true, with his pinpoint, inswinging cross finding the head of Merino, who nodded into the corner with the clinical touch of a veteran marksman rather than a central midfielder.
Just six minutes later, he produced an equally composed finish to tap Trossard’s cross home at the far post, securing the points.
This result means Arsenal are just four points behind league-leaders Liverpool, although the Reds do not play until Sunday afternoon against Wolverhampton Wanderers.
The Foxes, on the other hand, are still in the relegation zone, two points adrift of Liverpool’s opponents in 17th, having now lost each of their previous five PL matches ‘to nil’.