Lab Results suggest a significant “Stevens Effect” — improving players by half a win share or so per 48 minutes — may truly exist. But there’s nothing like field-testing. Tonight, the Brad Stevens theory faces a daunting challenge as the Celtics take on the Washington Wizards in the Garden.

Right now the Celtics training room looks like a *MASH* unit — or would, if there weren’t so many players making hospital visits or getting second opinions. Al Horford, Jaylen Brown, Marcus Smart, Daniel Theis, and Gordon Hayward — out Wednesday. Kyrie Irving doubtful.

Still available, however, are several Celtics with credible NBA starts, including Marcus Morris, Jayson Tatum (hopeful), Aron Baynes, Greg Monroe, Shane Larkin (minutes restriction), and Terry Rozier. (*ulp — at least at tipoff.)

Not to mention Semi Ojeleye, Kaedeem Allen, Guerschon Yabusele, and seemingly half of the Maine Bear Claws roster, as one wag put it on Reddit. (“Maybe they should wear Bear Claws jerseys to avoid confusion.”)

We’re actually looking forward to it. Brad Stevens and his wonderful chemistry set. He’s out-coached Scott Brooks before.

Three things to watch for

1. Un-small ball

With Monroe, Baynes, and Ojeleye playing more, and Horford’s spacing and fluidity not available, there may be more posting up. The Celtics may experience an improved offensive rebounding total as well. This approach comes at a potential price, namely opponent fast breaks of the offense stalls or turns the ball over. But if the Celtics score efficiently inside, they’ll not only slow the game — an advantage given a thin bench — but be able to get back and play their set defense more often. Then it’s win-win.

Look for lots of high-low post and cutters too. Monroe and Baynes — underrated as passers. Rozier, Tatum — excellent cutting instincts.

Guerschon Yabusele, back from the Maine Bear Claws, may be elevated to the starting lineup tonight. That’s the rumor as we file. It wouldn’t shock us. Stevens inserted Shane Larkin when Kyrie Irving missed the recent Bulls game, commenting that it helped the bench unit keep its rhythm.

2. Offensive role for Morris, Tatum, Rozier

Most Celtics fans would welcome a “Tatum unleashed” sighting. In fact, of course, Stevens has encouraged Tatum to keep taking those threes, which he does with rookie-record-setting efficiency — and get to the rim as well. But he is a rookie, and has now played about 3-4 times as many minutes as he did at Duke last year, or any previous season in high school.

Marcus Morris needs no encouragement to shoot the basketball, contested or not. It’s true that his effective field-goal percentage is lower on those contested mid-range shots (below 40% on two to six dribbles) than on catch-and-shoot (above 52 percent.) On open looks, Morris has been deadly.

And Terry Rozier — Scary Terry — is on an offensive tear that’s gone on too long to be a streak. Rozier’s true-shooting percentage is .585 since February 1 (15 games), lifting him to .529 for the year.

3. Semi Ojeleye

With Theis out for the year, and Horford temporarily, Ojeleye will be a key man for the Celtics. Stevens says he may see minutes defending opposing wings, power forwards, and even some 5s. He’s been stiff offensively, but hopefully can find a rhythm with extended minutes. If there’s a one-player test for the Stevens Theory, it’s Ojeleye.