Arsenal held Chelsea to a goalless draw in the first leg of their Carabao Cup semi-final on Wednesday night.
It was the Video Assistant Referee (VAR) system that took centre stage during a relatively uneventful affair at Stamford Bridge, as referee Martin Atkinson used the technology twice to assess two penalty shouts in either half, neither of which were given.
Chelsea had the better of the chances on the night, but could not break through Arsenal to leave the tie wide open heading into the second leg at the Emirates in two weeks.
For the second time, after Brighton and Crystal Palace met in the FA Cup on Monday night, the VAR system was being used in English football, and Atkinson wanted clarification on his decision not to award a penalty for a Victor Moses challenge on Ainsley Maitland-Niles in the 39th minute, which proved correct.
Chelsea did then come close to an opener on the stroke of half-time as a trademark deep cross from Cesar Azpilicueta found Cesc Fabregas in the box, but he could only head straight at David Ospina from an unmarked position.
The Blues came close again just after the break as they threatened from a short corner, but Andreas Christensen could only nod over from close range after Marcos Alonso had flicked a cross into his path.
Arsenal then suffered a blow just before the hour-mark when they lost Jack Wilshere, who was captain, to injury. It was an all-too familiar sight as the midfielder appeared to land awkwardly and hurt his ankle, before being replaced by Mohamed Elneny.
Arsene Wenger, who was serving the second match of his touchline ban from the Stamford Bridge press box, then threw Alexis Sanchez on for Alexandre Lacazette, with the substitution being jeered by a section of the away end.
There was some more use of the VAR late on as Danny Welbeck appeared to trip Fabregas in the box, but once again referee Atkinson’s initial decision was justified by the video replays.