For an entire month now, Manchester United’s mediocrity has been an open Premier League secret.

It’s been obscured by results, some of them very impressive, and excuses, some of them very legitimate. But it was apparent if you were paying close attention. It just needed somebody to expose it.

Enter, stage right, at the back post, Harry Maguire and Leicester City.

Juan Mata looked to have been the latest to drag the Red Devils to three points despite another lackluster performance, but the Foxes, down to 10 men, snatched a 94th-minute equalizer, and a 2-2 draw.

They punished United for its remarkable inability to put the game away, despite three or four golden opportunities to do so. In the waning minutes of the match, Leicester was as open as could be. United galloped end to end, outnumbering the seemingly defeated hosts. But its execution was incredibly poor.

Mata, the Spanish playmaker who has been in and out of Jose Mourinho’s team at irregular intervals, had led United’s comeback from 1-0 down to 2-1 up. He buried a clever equalizer in the first half, then a looping free kick in the second.

When Leicester substitute Daniel Amartey was sent off with 17 minutes remaining, United appeared to be home and dry.

And the Red Devils should have been. Anthony Martial, Marcus Rashford and Jesse Lingard all had one-on-ones with Kasper Schmeichel. Martial skied a shot over the bar. Lingard rounded Schmeichel, but fired off the post. Rashford tried to round the Leicester keeper, but lacked conviction, and the chance fizzled out and over the end line. The young winger appealed for a penalty, but didn’t deserve one.

In stoppage time alone, United had 2-v-1s and 3-v-2s. It had endless space to drive home a dagger. It somehow couldn’t. It was “childish,” according to Mourinho, who rued his players’ lack of maturity. “Childish in our box, and childish in their box,” he said. We were punished by our mistakes and what more can I say?”

And then Marc Albrighton sent a curling 50-yard cross to the back post. Chris Smalling – who had been down on the pitch, and then off it getting treatment, just minutes earlier – froze as Albrighton’s ball sailed over his head. Maguire slid in, and snatched a point.

“We were punished by our mistakes,” Mourinho lamented.

Questions will be asked about whether Smalling should have still been on the field; whether 10 vs. 10 would have been preferable to 10-and-a-half vs. 10. Questions will be asked about Ashley Young distancing himself from the scene of the crime, and David De Gea’s decision to stay rooted to his goal line.

But questions should be asked about United as a whole. Mourinho’s team wasn’t good enough to put the game out of sight. At one point, it was probably fortunate to have a lead in the first place. Its defenders were drowsy in the first half as Riyad Mahrez and Jamie Vardy broke for an opening goal:

Mata’s equalizer had the game where it deserved to be at halftime, level at 1-1. Leicester had the first glorious second-half chance to make it 2-1. Mahrez mesmerized Young on the right wing, and his cross trickled through to Christian Fuchs. Fuchs’ shot was blocked on the goal line.

United has held onto several one-goal leads over the past month without supplementing them. It beat Brighton and Bournemouth 1-0 at home. It beat CSKA Moscow and struggling West Brom 2-1. It hadn’t looked like the second-best team in the league on any of the four occasions, and hasn’t in a while.

It was therefore only a matter of time before the Red Devils were found out. They’ve now been exposed twice in a week, first by Bristol City in the League Cup, and now at the King Power. They fell 13 points behind Manchester City, and failed to distance themselves from the rest of the Big Six.

But it’s not just this result that’s worrying. It’s a pattern of wastefulness, perhaps even arrogance, and susceptibility. It’s only one loss. But if performances don’t improve, Mourinho’s men could find themselves in a real battle to even claim one of three available places in the top four.

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Henry Bushnell covers global soccer, and occasionally other ball games, for Yahoo Sports. Have a tip? Question? Comment? Email him at henrydbushnell@gmail.com or follow him on Twitter @HenryBushnell.