On the afternoon when the club’s top scorer for the past three years netted his 25th goal of the campaign to cement a place in the League One play-offs, the operator of the Keepmoat Stadium sprinkler system also revealed an ability to deliver at the optimum moment.
Having watched around 100 or so Coventry fans invade the pitch at full-time and then clash with baton-wielding police, said operator waited until these idiots had returned to the goalmouth in front of the away seats before unleashing two powerful jets of water from the turf.
The moronic interlopers and their Stone Island jackets getting an unexpected soaking took the sting out of the trouble in a similar manner to how Marquis, just a few minutes earlier, had finally killed off Peterborough United’s hopes of pipping Rovers to sixth place.
Grant McCann’s men were a goal ahead at the time thanks to Kieran Sadlier’s first-half header.
But there was still a palpable sense of nervous tension in the air. Every single one of the home fans in the 12,794 crowd knew that a Coventry equaliser at such a late stage would lead to the initiative firmly swinging the way of a Posh side who were ahead against Burton Albion at London Road.
So, when Marquis responded quickest after Lee Burge had blocked his initial header to fire the rebound into the gaping net, the timing really could not have been better.
Hence why manager Grant McCann hailed the 26-year-old as “the best number nine in the league” after Doncaster had booked a two-legged semi-final with Charlton Athletic.
“John sets the tone for us,” said the Rovers chief. “No-one works like him, no-one runs like him and no-one has his aggression. To get 25 goals is a phenomenal return.
“But I know he will be thinking, ‘I have three games to go, I can get another three or four’. That is the way he thinks.
“He worked so hard all afternoon. The chance came along at the end and it was a good header, and follow-up.”
On the achievement of reaching the play-offs, McCann added: “I never slept on Friday night. I am not sure if that was nervous tension or excitement but I struggled to get off to sleep.
“We wanted to get that top-six place. We owed it to our fans, who came out in big, big numbers.”
After being the unwitting hosts to final-day promotion parties involving Wigan Athletic and Burton in the previous three years, Doncaster were determined the climax of the 2018-19 campaign would see the Keepmoat reverberating to the sound of their own celebrations.
Rovers duly delivered, though only after an opening quarter in which Coventry had made clear the hosts would not have it all their own way.
Mark Robins’s Sky Blues arrived in south Yorkshire having taken 10 points and scored 11 goals in their last five games on the road.
But for a perfectly-executed tackle by Danny Andrew on Brandon Mason just as the Coventry man looked to be through one-on-one with Marko Marosi, that goal tally could easily have been swelled to a round dozen inside just two minutes.
With Jordy Hiwula in lively form, plus both Luke Thomas and Amadou Bakayoko bringing a tremendous athleticism to the City attack, Doncaster looked vulnerable.
Eventually, though, the hosts rediscovered the attacking verve that has characterised much of the season at the Keepmoat.
There was more discipline to Rovers’ play than usual.
Malik Wilks, for instance, spent a lot of his afternoon before being substituted near the end playing deep enough on the right flank to be within touching distance of full-back Matty Blair.
But when an opportunity came along to hurt Coventry, McCann’s men did not hold back.
Never was this more apparent than when Wilks made a foray down the right flank just after the half-hour.
The on-loan Leeds United man, after collecting possession near the corner flag, displayed fine technique to create sufficient space to whip over a cross that left goalkeeper Burge horribly wrong-footed.
Kieran Sadlier gleefully took advantage, the January signing from Cork City powering a header into the unguarded net.
Rovers had started to hit their stride a few minutes earlier. A sublime 40-yard pass from the evergreen James Coppinger had found Marquis on the edge of the penalty area only for the London-born striker’s shot to be saved.
But, once ahead, there was a different, more controlled, feel to the home side’s play as the first half ended with Wilks bringing a save from Burge and Marquis’s drilled effort from 20 yards flashing just past the post.
The chances dried up initially after the restart but, again, Doncaster refused to panic. Their reward for such patience came when Marquis, having initially been denied by Burge, was on the rebound like a flash to not only net his 66th goal in Rovers colours but also get the party truly started.
Doncaster Rovers: Marosi; Blair, Downing, Butler, Andrew; Whiteman, Kane; Wilks (Crawford 70), Coppinger (Smith 82), Sadlier (Rowe 82); Marquis. Unused substitutes: Jones, Anderson, Lewis, May.
Coventry City: Burge; Sterling, Hyam, Willis, Mason; Kelly, Shipley (Ponticelli 74); Thomas, Enobakhare (Chaplin 44), Hiwula; Bakayoko (Westbrooke 56). Unused substitutes: Addai, Drysdale, McCallum, Wakefield.