Crawley Town have been relegated to League Two with a final-day heartbreaking home defeat.
Reds needed to win to secure their place in the division next season, but suffered a 2-1 home reverse to the fellow relegation threatened Sky Blues.
It was a dramatic climax to the season with Dean Saunders’ sides at one point holding 18th place thanks to Mathias Pogba’s opening goal in the second half.
That came after Brian Jensen saved a penalty on the stroke of half-time, but Coventry equalised through Marcus Tudgay and James Maddison hit an injury-time winner to condemn Reds to the drop along with Notts County, Leyton Orient and Yeovil.
It ended Crawley’s three-year stay in League One and was a cruel end to day which had brought out a record crowd of 5,744 at the Checkatrade.com Stadium - although Reds would have only been safe with a win.
Saunders stuck by the same team that suffered a last-gasp defeat away at Peterborough last week as he named an unchanged side.
Both teams went into the game knowing the three points would be enough to ensure their future in League One, although other results meant the Sky Blues would have stayed up even with a defeat.
Coventry had the ball in the net on five minutes, but it was ruled for a foul on Brian Jensen.
John Fleck’s left-footed free-kick from wide right was collected by the Reds stopper and he fumbled into the net under pressure, but the whistle had gone for a infringement on the stopper.
Moments later, Fleck got the visiting fans on their feet again as he drilled just over the bar from the edge of the box.
At the other end, Reds started to get into the game as a Lee Fowler free-kick was well defended and Youga fired over the bar from range.
The pressure swung fully to the home side as a couple of dangerous free-kicks required the Coventry defence to earn their crust, while Lee Burge collected a high dangerous ball across the goalmouth.
O’Brien found himself in the referee’s notebook on 18 minutes as he chopped down Lewis Young, who had skipped away from him on the right.
The visiting skipper was quick to point a finger at his opposing full-back saying he had dived, much to the annoyance of the Crawley fans in the Bruce Winfield Stand.
Two minutes before the break, Reds’ best move saw Young get up in support of Fowler and his inch-perfect pass put Marvin Elliott in, but his low shot from a tight-angle was well held by Burge.
On the stroke of half-time, however, Gavin Tomlin allowed Marcus Tudgay get the wrong side of him in the box and gave away a penalty.
But fans’ favourite Jensen was down superbly to push away Nick Proschwitz’s effort from 12 yards much to the delight of the home crowd - continuing the Sky Blues’ poor record of scoring just one of their last five spot kicks.
As the sun came out for the second half, the roof came off the stadium as Pogba headed Reds ahead within four minutes of the restart.
He rose highest at the far post to nod home Tomlin’s cross past a static Burge. Chants of ‘we are staying up’ rang out as McLeod went through moments later, but his effort was well saved by Burge.
Substitute Maddison’s free-kick on 64 minutes fell as far as O’Brien but his fierce effort from the edge of the box was blocked by Josh Simpson.
The visitors were the ones putting the pressure on and it told on 73 minutes as O’Brien’s whipped cross from the right was headed into the top corner Tudgay to level the scores and drop Reds back into the bottom four.
Disaster struck for Crawley on 90 minutes as they pushed forwards, a mistake from Darren Ward saw him pick pocketed by Frank Nouble, who squared for Maddison to smash home and break Crawley hearts.
Crawley: Jensen, Youga (Edwards 82), Bradley, Ward, Young (Oyebanjo 70), Fowler, Tomlin, Simpson (Bawling 82), Elliott, McLeod. Pogba. Unused subs: Price, Smith, Morgan, Harrold.
Coventry: Burge, Willis, Johnson, Martin, Stokes, Fleck, Ward, Barton (Maddison 54), O’Brien (Webster 91), Proschwitz (Nouble 61), Tudgay. Unused subs: Charles-Cook, Jackson, Odelusi, Phillips.
Attendance: 5,744 (1,700).