The Red Devils striker was absent from the lineup on Sunday due to a knee injury, but Samuel Luckhurst of the Manchester Evening News reported there was good reason behind his Etihad Stadium appearance.
The report noted manager Louis van Gaal usually doesn't permit players not in his squad entry to the dressing room, but special exception was made for Rooney as he attempted to inspire his team-mates.
It appeared to have the intended effect, as Marcus Rashford continued his fine run of goals in the senior ranks with a 1-0 winner, and Rooney was full of praise for the youngster's performance after the result:
Wayne Rooney @WayneRooney
Massive 3 points yesterday. Congrats to Marcus Rashford on another great goal & first in a derby. Brilliant lads 🔴🔴🔴 https://t.co/aM3zQMKCO92016-3-21 10:21:28
It's particularly poignant that Rashford should take on the role of United hero in the triumph over City, considering Rooney may now face a fight to reclaim his starting berth from the 18-year-old when he's fit again.
Luckhurst also provided quotes from Rooney when he was quizzed on his leadership role and approach to speeches last May during an interview with former team-mate Gary Neville.
Regarding his dressing-room talks, the 30-year-old said:
I've done a few to be honest throughout the season, a few players spoke about one in particular , we'd just got beaten in the FA Cup at home to Arsenal, so we were out of literally everything.
Our main aim was to finish as high up in the table and then we had Liverpool coming up, Man City coming up, so I knew we had some tough games and as a reminder to the players [I told them] the football club we're playing at, the standards you need to set at this club and what we have to do to reach our goal from then until the end of the season.
Rooney acknowledged the fact it was his "job" as captain to motivate his men to success, and while he may not be able to have his influence on the pitch at present, it isn't stopping him from leading from the sidelines.
It's particularly pleasing for Van Gaal to see English players developing at Old Trafford, as Match of the Day highlighted the recent influence of Rooney, Rashford and Jesse Lingard in front of goal:
Match of the Day @BBCMOTD
Six of Man United’s last seven PL away goals have been scored by English players. #MOTD2 https://t.co/EIrazDOwqp2016-3-20 23:27:13
One might suggest Rooney may be more effective as a speaker than on the pitch, with United winning five of the eight Premier League games they've played without their captain this term, equal to a win percentage of 62.5 per cent. That's compared to the nine games they've won from his 22 appearances, equal to a win percentage of just 40.9 per cent.
The Red Devils will assuredly savour the veteran's return all the same after the international break, and perhaps Van Gaal will consider looking to his leader for inspiration more often in future.