Ben Simmons' frailties at the free-throw line were exposed and Joel Embiid injured his knee as Philadelphia blew their chance at a first NBA playoffs sweep in 30 years.
The 76ers lost 122-114 to Washington, to lead their Eastern Conference first-round series 3-1.
If losing Embiid late in the first quarter wasn't bad enough, Simmons compounded Philadelphia's woes with an abysmal return from the free-throw line.
In Embiid's absence, the Wizards employed deliberate fouling tactics on Simmons and they were rewarded when the Australian could only convert five off his 11 free throws.
A back-and-forth fourth quarter was tight down the stretch after Danny Green's lay-up with about 4 minutes and 30 seconds to go made it 106-all.
That's when Washington basically took the ball out of Philadelphia's hands, sending Simmons to the line repeatedly with a version of the old Hack-a-Shaq strategy that Shaquille O'Neal used to face.
"Obviously that's what they're going to do. That's what they should do," Philadelphia coach Doc Rivers said. "And I'm OK with that."
Simmons came into the night 0 for 9 on free throws in the series and was 1 for 3 for the night before Hack-a-Ben went into full effect.
Asked by a reporter about keeping Simmons in the game while Washington repeatedly fouled him, Rivers replied: "You want me to take Ben Simmons off the floor? No. He's pretty good. I'll pass on that suggestion."
Simmons finished with 13 points and 12 rebounds after Embiid fell awkwardly on a drive to the basket in the opening term and was ruled out of the remainder of the game with knee soreness.
"Obviously, we need Joel to win. He's a big part of this team," Simmons said.
The four-time All-Star centre had eight points and six rebounds in his 11 minutes after erupting for a career playoff-high 36 points in the 76ers' 132-103 win in Game 3.
After staying down for a moment, a wincing Embiid rose and then put his hand on his lower right back.
Russell Westbrook's 12th career playoff triple-double and Bradley Beal's 27 points helped the Wizards stave off elimination.
The top-seeded 76ers, who were bidding for their first sweep since eliminating Milwaukee in a best-of-five, first-round series in 1991, can advance with a home win in Game 5 on Wednesday.
Joe Ingles' Utah Jazz, the team with the NBA's best record in the regular season, are on the verge of closing out their first round, best-of-seven series against the Memphis Grizzlies.
With Donovan Mitchell scoring 30 points, the top-seeded Jazz grabbed a 3-1 lead to hold off the Grizzlies 120-113.
All-Star Rudy Gobert scored 13 of his 17 points in the third quarter.
Jordan Clarkson scored 24, Bojan Bogdanovic added 13 and Mike Conley had 11.
Game 5 will be played in Salt Lake City on Thursday morning (AEST).