Just over five minutes into the first game of the 2017-18 NBA season, Gordon Hayward went up to catch a lob pass. The ball sailed out of reach, and Hayward crashed to the floor, dislocating his ankle and fracturing his tibia. Whatever faint title aspirations the Celtics may have harbored for this season ended with that play. The main question now is whether Hayward will be able to make a full recovery, and we likely won’t find out this season. The short-term question is easier to answer, and more urgent: Just how bad is it going to get?

To figure out what fans can expect from the remaining 81 games, I used FiveThirtyEight’s revamped CARMELO projections to redistribute Hayward’s 30 or so projected minutes per game to the rest of the expected rotation. As you would guess, the new projection was ugly: 37 wins — 10 less than our initial 47-win prediction for Boston, which was already low compared to the team’s preseason expected win total according to Vegas lines (about 53.5 wins). Forty-seven wins would have been a disappointment; 37 would be a catastrophe, and it would likely mean missing the playoffs.

How the Celtics line up without Hayward The Celtics’ projected performance (now that Gordon Hayward is out) based on FiveThirtyEight’s CARMELO player projections PLAYER MIN. PER GAME OFF +/- DEF +/- Kyrie Irving 34.0 3.9 -2.1 Jaylen Brown 29.0 -1.9 -0.7 Marcus Morris 29.0 0.0 0.0 Al Horford 28.0 0.1 1.6 Marcus Smart 34.0 0.5 0.6 Jayson Tatum 26.0 -1.4 -0.7 Aron Baynes 10.0 -2.5 1.1 Terry Rozier 19.0 -0.7 -0.8 Shane Larkin 12.0 -0.5 -1.6 Abdel Nader 5.0 -1.7 -0.3 Guerschon Yabusele 5.0 0.5 0.0 Semi Ojeleye 8.0 -1.9 -1.8 Replacement level — -1.7 -0.3 Team total — -0.1 -1.8 PROJECTED RECORD W L 36.6 45.4

The only halfway comforting thing about this projection for Boston is that a lot of that falloff is wrapped up in conservative projections for two players: Jaylen Brown and Jayson Tatum, the team’s high-lottery selections from the past two drafts. Tatum is 19 and Brown turns 21 next week, so this isn’t really a surprise, but Hayward’s injury forces Boston to rely on two young players who may not be ready and hope that one or both can grow up fast. It’s probably a reach to expect too much out of Tatum in his first year, but Brown played well at times down the stretch last season and had a few solid appearances during the playoffs. Brown also scored a career-high 25 points in Tuesday night’s loss, flashing to the rim and being a pest on defense. If Boston salvages its season, it will need a lot more games like that.

Brown is a polarizing prospect around the league. He had an uneven season in his first year, and he lacks the polish of Tatum, who was the third overall pick in this year’s draft out of Duke. Brown isn’t a great shooter or passer and doesn’t score with the efficiency teams hope for from their peripheral players, but he’s already a capable perimeter defender and the sort of top-shelf athlete who looks at home banging bodies with LeBron on national TV. He has a long way to go, but so did Paul George when he logged a rookie season not so different from Brown’s.

Equally important as Brown’s potential is the fact that his projected contribution this season is absolutely terrible, coming in slightly below replacement level (meaning he’s expected to be a little worse than any random free agent a team could sign off the street). Minute to minute, CARMELO believes that he contributes about as much, offensively and defensively, as Knicks’ backup guard Ron Baker. So he wouldn’t have to do much to outperform his expected level.

Given how many minutes Brown was expected to play — and how many more he’ll have to take on now that Hayward is out — that projection weighs down Boston’s expected win total considerably. For instance, if Brown were to improve his average offensive and defensive contribution to the level of fourth-year guard Marcus Smart, the team, even without Hayward, would project to win about 42 games. If he improved just a bit more — say, to the level of departed swingman Jae Crowder — that number creeps up to 43 wins. Still not what Boston had in mind coming into this season, but a far cry better than 37 wins and out of the playoffs.

How the Celtics line up if Jaylen Brown exceeds expectations The Celtics’ projected performance (now that Gordon Hayward is out) based on FiveThirtyEight’s CARMELO player projections, assuming Jaylen Brown plays as well as Jae Crowder PLAYER MIN. PER GAME OFF +/- DEF +/- Kyrie Irving 34.0 3.9 -2.1 Jaylen Brown 29.0 1.2 0.7 Marcus Morris 29.0 0.0 0.0 Al Horford 28.0 0.1 1.6 Marcus Smart 34.0 0.5 0.6 Jayson Tatum 26.0 -1.4 -0.7 Aron Baynes 10.0 -2.5 1.1 Terry Rozier 19.0 -0.7 -0.8 Shane Larkin 12.0 -0.5 -1.6 Abdel Nader 5.0 -1.7 -0.3 Guerschon Yabusele 5.0 0.5 0.0 Semi Ojeleye 8.0 -1.9 -1.8 Replacement level — -1.7 -0.3 Team total — 1.8 -0.9 PROJECTED RECORD W L 43 39

This is of course a sort of tautology: If Boston’s players play better, we expect them to win more games. And there isn’t much point in using projections if we throw them out whenever it’s convenient. But in this case, the Celtics’ fortunes are tethered to just the sort of prospect who is capable of making a leap ahead of where his past performance would imply he’ll be.

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