Sunday afternoon as Jayson Tatum shut down the doubters — and I’m one of them — a thought crept across the minds of many Celtics fans.

Beat LA.

Naturally it’s a little bit premature. Not only do the Lakers have to get through the Western Conference’s best team in the Denver Nuggets, but the Celtics better not be looking ahead either. Wednesday night’s NBA Eastern Conference final foe, the Miami Heat, could spoil this party.

There’s no question the Celtics are better than Miami. Yes, “Playoff” Jimmy Butler is amazing, he’s averaging 31.1 in the playoffs. Bam Adebayo is a force. And Erik Spoelstra is far and away the best coach remaining in these playoffs.

But Victor Oladipo was lost for the season with a playoff knee injury. And last year’s best sixth man/eccentric sharpshooter Tyler Herro, who averaged more than 20 ppg this season, broke his right hand 19 minutes into the playoffs and is extremely unlikely to be ready at any point in this series.

The 50,000-foot view is that despite whatever Spoelstra cooks up, and Butler delivers, Boston is still way better on paper. On parquet, too. The Celtics have lived on the edge in letting Atlanta push them to 6 games and the Sixers to Game 7. More of this, and as the second half of the phrase goes, they will “find out.” At worst, this series should be over in five games.

But does anyone trust these guys?

Tatum’s last five quarters of action have been the peak of his enormous potential. If that Tatum is here, there will be enormous buzz June 1 at TD Garden for the first game of the NBA Finals. But Tatum acutely represents the maddening inconsistency of this team. When he’s on, when they’re on … they actually should hope to play LeBron James and the Lakers. They are better.

But when Tatum is in a funk, the team follows the leader there, too. Jaylen Brown can be a matchup nightmare for the Heat, depending on how Spoelstra plans to defend him. Butler will want to get in Tatum’s jersey and Butler is a known irritant. He will try and get in Tatum’s grille. Does Adebayo check Brown? That carries some risk for Miami.

Even if those are the moves and they work, though, then what? Miami had a bad offense even with Herro and Oladipo. Where are their points coming from? Even if Butler goes nuts (and he likely will), is anyone worried about getting lit up by the corpses of Kevin Love or Kyle Lowry? Max Strus, Maine man Duncan Robinson, and Gabe Vincent can all shoot threes, but Robinson has only gotten playoff PT because of the injuries to others.

Suggestion for Celtics boss Joe Mazzulla: Let Jimmy cook.

Yes, they will try and make life hell for Butler, but if you go all-in to stop him it might mean he averages 29 ppg instead of 35. Jimmy’s gonna get his.

What the Celtics cannot do is let some spare scorch them with threes, the great equalizer. Miami can only win if they get some major unexpected contributions. Don’t let them.

Fans should root for a Finals against LA, absolutely. Mostly because they could eat LeBron’s lunch. They would have a much bigger problem with Denver. But that’s down the road.

For now, the Celtics need to hone that killer instinct. It cost them last year when they tuckered out against Golden State after being dragged to seven games in the second round against Milwaukee, and seven games in the ECF against … Miami.

There are no excuses. Boston just has to make that last, long step. And that starts by playing a full 48 every time now.