The Boston Red Sox won 108 games this year, the most in the team’s history. Mookie Betts, their star outfielder, won the American League batting title (hitting .346), stole 30 bases, and led the league in extra-base hits, including 32 home runs. The last year someone led the AL in both batting average and extra-base hits was 1956—and that player was Mickey Mantle.

Betts is just one of the Red Sox weapons. J.D. Martinez hit 43 home runs and led the AL with 130 runs batted in. He hit .330, not far behind Betts. In general, the Red Sox have a strong lineup: Andrew Benintendi, Xander Bogaerts, Mitch Moreland, and Brock Holt are all dangerous (though Moreland has been terrible of late). The team’s defense is 7th in the majors in fewest errors. They run and steal bases with as much wisdom as any team in baseball. Their top starting pitchers, David Price and Chris Sale, are two of the best in today’s game. And while closer Craig Kimbrel hasn’t looked as strong as he did last year, he still had 42 saves and an ERA of 2.74.

And with all of that said, Red Sox Nation should be worried.

Born and raised in Rhode Island, I’ve loved the Red Sox since I was child. In 1986, when I was 10, I watched them lose Bill Buckner’s Game 6 against the Mets with a knitted blanket over my head the entire time, because I couldn’t bear to see the doom that was clearly approaching. When the Sox lost the ALCS to the Yankees in 2003—after being so close—I assumed the curse was eternal. Which is what made 2004’s miracle comeback against the Yankees, capped by their first World Series title since 1918, so unbelievable.

Since then Red Sox fans have been blessed. There were two more titles, in 2007 and then again in 2013 with a team that was full of characters and included one of the great World Series performances, ever, as David Ortiz went 11-for-16 with two home runs and six RBIs against the Cardinals.

On paper, this year’s Red Sox team is probably better than the 2013 squad. But they have flaws.

In the last two months, the bullpen has weakened, from relief to closing. Aside from Price, the entire starting staff has struggled of late. Rick Porcello has 17 wins, but his ERA is over 4. As for Sale, he has been given fewer innings so that he can recover from shoulder inflammation. He’s pitching slower and doesn’t look like himself. He’ll start Game 1 against the Yankees, but it’s unclear how long he can last. (Manager Alex Cora said of Sale, “I’m 100 percent sure he’s healthy and he’s going to be fine.”)

The bullpen has picked up some bad habits along the way: too many walks and too many hits. In September, their ERA was just under 5.00 (it’s been over 4 since July 31). And not one of Boston’s relievers looks unhittable, as several relievers do on the Yankees, Astros and Indians. The Astros won 103 games in the regular season, the Yankees 100, and the Indians 91. The Red Sox are the favorites, but there are no cupcakes in the American League this year.

And then there's Price. He has been nearly perfect since the All-Star break, but as Jared Diamond, my colleague at the Wall Street Journal, recently wrote, Price has struggled in the playoffs. In 17 post-season appearances, his ERA is 5.03. That’s worse than all but one pitcher among those with a minimum of 60 postseason innings. (That man: former Red Sox knuckleballer Tim Wakefield.)

When the best-of-five contest begins Friday night, I’ll be hoping for the best as the Sox take on the Yankees. This is baseball’s 100th division series contest and the first time both teams in the division round have won 100 or more games. It’s going to be a war.

And the best team in baseball could be in trouble from the start.