When Joakim Noah underwent knee surgery four weeks ago, there was hope — however faint — that he’d be able to suit up for the Knicks again this season. He could very well be ready if they made a playoff push, the Knicks said at the time, holding on to that fading glimmer of possibility.

Noah then was caught using a performance-enhancing drug and faces a 20-game suspension, but the Knicks believe their center could be returning to practice very soon.

Why does it matter? Because the sooner Noah can get cleared, the sooner he can start serving his suspension, reducing the number of games he’ll have to serve next season.

“It was kind of the plan after that road trip to take a look,” Jeff Hornacek said before the Knicks beat the Pistons, 109-95, on Monday night at Madison Square Garden. A loss would have eliminated the Knicks from playoff contention.

Derrick Rose led the Knicks (28-46), who had lost five in a row, with 27 points and 12-for-17 shooting. Kristaps Porzingis had 25 points and eight rebounds and Carmelo Anthony scored 21 points in his return to the lineup after a two-game absence.

“Doctors are taking a look at him tonight and we’ll see if he can get back to practice,” Hornacek said of Noah. “I think if that’s the case, then he practices tomorrow, and I think the NBA has to clear it or whatever . . . we’ll see.”

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“I feel bad for his situation,” Anthony said. “I don’t really know too much details. I’ve talked to him. It’s a situation he’s going to have to handle himself . . . Whatever challenge that’s out there that’s in front of him, I think he’s kind of ready to man up and face them.”

There is absolutely zero illusion that Noah immediately would be NBA-ready after sitting for four weeks. “He may not be in great shape,” Hornacek said. However, getting cleared to practice Tuesday would mean that the clock on his suspension could begin as soon as tomorrow’s game against the Heat.

That would leave 12 games for him to serve next season, the second in a four-year, $72.5-million commitment that is looking worse by the second.

Noah was paid $17 million in this injury-ravaged season for 46 games’ worth of service in which he averaged 5.0 points, 8.7 rebounds and 0.8 blocks.

On Saturday, the NBA announced that Noah had tested positive for Selective Androgen Receptor Modulator LGD-4033, a non-steroidal drug that the players association said he unknowingly ingested. Hornacek said he does not believe the supplement was supplied to Noah by the Knicks’ training staff but added that he knew nothing about it.

“Most of these guys, I think if they want to do something on the side, some sort of supplement, I think they check with our trainers and the trainers analyze and take a look at it,” he said.

“But again, sometimes you can’t control these guys if they’re taking other supplements they buy at the store or something. It’s kind of beyond them to make sure [that supplements aren’t tainted].”

Hornacek said he spoke to Noah at the training facility Monday morning but would not disclose what was said. Asked about Noah’s mental state, Hornacek responded that there is “nothing you can do about it.”

“He’s going to miss some games,’’ he said, “but he’s committed to getting back and playing, and whatever the games he has to miss, he’s ready for that and his focus will be when he gets back on the floor, helping us win games.”