Professional bettors aren’t ready to buy Boston until they see Sale.

Chris Sale of the Red Sox enters Friday night’s Divisional Series opener with the Yankees at Fenway Park with only 17 innings of work in his game log since the end of July. Five total appearances, none lasting longer than five innings.

Sale has been battling shoulder inflammation. That could be a blessing in disguise because he’s had a career history of fading down the stretch from fatigue. That won’t be an issue this year.

But it’s far from clear that he’s overcome inflammation issues beyond his manager saying everything will be fine. If Sale isn’t at 100 percent, then Boston is no longer the true favorite to win the American League regardless of what the regular-season records and futures odds suggest. Boston is priced as if he’s going to be a major force. Look at how mortal the rest of the starting rotation rates in an analytics stat respected by sharps.

xFIP for likely Red Sox playoff starters

For those not familiar with xFIP, it’s a “fielding independent” stat designed to represent a pitcher’s skill set on a scale that aligns with ERA. If you grew up with earned run average, xFIP better captures talent on a scale that’s already ingrained.

Sale is an elite Cy Young caliber hurler even when not backed by a great offense or bullpen. The others are much less able to control their own destiny with their stuff. That’s going to matter in a series where both home ballparks favor hitters.

Given lengthy time off since Sunday’s end of the season, a healthy Sale is positioned right where Boston wants him. He opens the Yankees series. He would be able to come back to pitch again if the best-of-five goes the distance. If Boston wins quickly, Sale would be ready to go in Game 1 of the ALCS.

But a Sale that isn’t 100 percent? Then, he’s just another arm in a vulnerable rotation (by playoff standards). If he can’t go at all beyond Friday’s “reset”… then it could get really tricky for the Red Sox fast.

Pro bettors rarely bet chalk in the baseball playoffs unless stars are aligned for a slightly mispriced juggernaut. They enter this October looking to either fade Boston, or bet other contenders at value prices. If you’re betting the Yankees Friday, or to win the series, many sharps are on your side already.

They’re also looking to bet Over in “first five-inning” props in any game with a vulnerable starting pitcher. If you like rooting for runs, but are impressed with these bullpens, that’s something for you to consider as well in this much-anticipated rivalry renewal.