A proud old pro banked home a 20-footer to give the No. 5 seed a series lead on a day when its best player didn’t play. A bunch of young pros might well have given the No. 1 seed a desperately needed jolt of pride.

In excruciating fashion, the Hawks lost a game they didn’t deserve to win but came unbelievably close to stealing. Down 91-70 and having been outclassed by the Washington Wizards, who were working without John Wall, the Hawks rallied behind a lineup of Dennis Schroder, Shelvin Mack, Mike Scott, Kent Bazemore and …

Mike Muscala.

Mike Muscala, the guy who spent the season shuttling between playing games in the NBA Development League and sitting the bench for the parent club. Mike Muscala, who got minutes near the end of the regular season when the starters were resting. Mike Muscala, whose outrageous 3-pointer with 14.1 seconds remaining tied a game that had been a blowout only eight minutes earlier.

OK, so it ended badly for the visitors. Paul Pierce did as Paul Pierce does, rising over the smallish Schroder to bank home the winner at the horn. Technically that puts the Wizards ahead 2-1, but somehow this sort of defeat — as opposed to lopsided kind, the kind the Hawks were about to suffer — felt as if something had been gained in losing.

Said coach Mike Budenholzer: “The way that the group that finished played, we’re going to have to play more like that for 48 minutes.”

What happened over the first 3 1/2 quarters of Game 3 here Saturday was shocking and shameful. The Hawks were being outplayed, which shouldn’t have happened, and outfought, which cannot happen.

OK, so some nights the shots don’t fall. (They haven’t for long stretches this postseason.) But effort should be a constant, especially in the playoffs. The 60-win Hawks were acting as if it were March again, and they were more concerned with resting people than winning games.

Odd things can happen in the playoffs, but what the Hawks did for 3 1/2 quarters Saturday was beyond weird. That’s because they didn’t do much of anything. They stood around. They watched the home team run figure-8s around them. They seemed helpless and, even worse, they seemed not to mind.

The Wizards had every reason to duck their heads and go quietly once the severity of Wall’s injuries — five non-displaced fractures of the left hand/wrist — were finally learned, but this unassuming bunch showed Saturday that it plans to make the Hawks work for everything. The Hawks, alas, were disinclined to work

With three days to rest and no Wall to defend, the Hawks should have landed the first punch Saturday and kept swinging. Instead they pressed Pero Antic into service for the ailing Paul Millsap — who would work 14 first-half minutes as a sub — and saw the emergency starter hoist three of their first five shots. All three missed. By then the Wizards were off and whizzin’.

The home side led by 12 points in the first quarter, by 18 in the second, by 19 after three quarters, by 21 in the fourth. This was total domination by a team that shouldn’t be dominating any No. 1 seed anywhere.

Two second-quarter plays were embarrassing — not because the Wizards made them but because the Hawks seemed content to let them. Otto Porter Jr. missed a wild drive and then, knowing he’d messed up, outfought everyone for the rebound and flipped home a less-wild reverse layup. Then Nene fumbled the ball, seized it back and barged down the lane for a three-point play.

Coaches call those hustle plays, and the East’s top team was being outhustled. And then it changed. Budenholzer went with his subs because he was looking for effort. He almost stole a game. Some will fault the coach for not bringing back all his starters when it became clear the Hawks had a chance to win at the end — he did bring back Kyle Korver and then, albeit briefly, DeMarre Carroll — but I won’t.

The subs were the only Hawks who acted as if they wanted to play Saturday. They deserved the chance to see if they could finish what they improbably started. They couldn’t quite, but they did this team a great service. They showed it what can happen if you try hard.