In reality, neither club broke any rules and will progress to the quarter finals without issue, despite the tabloid's best effort to create a problem where one didn't exist.
Carabao Cup Roundup: City Scrape Past Wolves as Bristol City Smash Palace & Leicester Progress https://t.co/f8PXJp84rL— ArsenalPro (@ArsenalPro) October 24, 2017
The unnecessary scandal emerged when the Gunners sent on Joe Willock in the 114th minute of their 2-1 extra-time win over Norwich, and when City used Kyle Walker in the 103rd minute of their game against Wolves that was eventually won by a penalty shootout.
Each club had already used the usual allotted three substitutes and so some who were happy to gloss over or ignore the rule changes to the League Cup this season for the sake of outrage chose to label it as some kind of cheating.
Section 10.2 of the official competition rulebook clearly states: "Where any match goes to extra time (in accordance with the provisions of Rules 14.4, 14.5 and/or 14.6), then subject to the League having obtained the prior approval of the International Football Association Board (IFAB) to the application of this Rule, each Club participating in that match will be permitted to use an additional substitute (in extra time only)."
Rules 14.4, 14.5 and 14.6 relate to the need for extra-time, and both Arsenal and City took full advantage of their right to use a fourth substitute during the additional half hour.
Perhaps where confusion initially emerged was that the Premier League pair made two substitutions each during extra-time, with City also making one at the end of the original 90 minutes. However, making multiple substitutions each during extra-time was not in contravention of the rules because each still hadn't used up their initially allotted three, before making a fourth.
The timing of the first three substitutions is completely irrelevant, as long as a fourth substitution is only made during extra-time.