D.C. United remained in sixth place in the Eastern Conference, but moved just two points behind fourth-place Philadelphia.
Sam used a diagonal run to get to Luciano Acosta's chipped ball inside the box and then did a half turn to finish with his left foot. The duo had a give-and-go in the 61st minute, but goalkeeper Steve Clark came out of his area and Acosta's shot went just wide.
Sam was subbed off for Neagle in the 72nd minute.
Neagle finished from distance in the 86th and four minutes later, Neagle won a long ball from goalkeeper Bill Hamid down the right sideline, dribbled into the box and found Alvaro Saborio near the penalty spot.
It was United's second win in the last 10 meetings with Crew SC.
Matteo Mancosu set up first-half goals from Dominic Oduro and Ignacio Piatti and the Montreal Impact beat the San Jose Earthquakes 3-1 to snap a four-game winless streak.
Johan Venegas added a goal in stoppage time to help the Impact win for the first time since a 2-1 victory in Toronto on Aug. 27. It was the first time in 11 matches that Montreal scored more than one goal.
Chris Wondolowski scored for San Jose. The Earthquakes are winless in seven games.
San Jose wasted a chance to tie it at 2-2 in the 87th minute when it was awarded a penalty kick after Laurent Ciman fouled Shea Salinas, but Evan Bush dropped to the ground to stop Wondolowski's low shot.
In injury time, Venegas tapped in his first goal of the season off a feed from Piatti.
Toronto FC regained the Eastern Conference lead in a 0-0 draw with Orlando City.
It was the third straight draw at BMO Field for Toronto, extending its unbeaten streak to four. Greg Vanney's team has lost just once in 12 games. But it has not won at home since Aug. 6.
Toronto played the last 20 minutes a man down after Tosaint Ricketts got a second yellow card. Referee Alan Kelly ruled that Ricketts' boot made contact with Uruguayan defender Jose Aja during an attempted bicycle kick.
Orlando had lost its last three matches, giving up four goals in each.
Chad Marshall headed in a corner kick in the 24th minute and the Seattle Sounders beat the Chicago Fire 1-0 to get back into the MLS playoff picture.
The Sounders have 41 points and climbed into a tie with idle Portland for the sixth and final playoff berth in the Western Conference. Seattle still has one game at hand on the defending champion Timbers, and also has one more win. Total wins is the first tiebreaker.
Chicago was eliminated from postseason contention. The Fire have four games remaining and can finish with no more than 39 points. D.C. United is sixth in the East with 40 points after beating Columbus earlier on Wednesday.
Andreas Ivanschitz set up Marshall's fourth goal of the season with a corner kick from the right wing side. The ball floated to the top right corner of the six-yard box and Marshall went up with a twisting header that went into the far side of the net, way beyond the reach of goalkeeper Sean Johnson.
Video via MLS: DC United 3-0 Crew SC
DC United put three goals past Columbus in the final 20 minutes, putting themselves in great position in the playoff hunt.
Video via MLS: Montreal 3-1 San Jose
Evan Bush stopped a penalty kick from Chris Wondolowski in the 87th minute to guarantee the Impact three points against San Jose.
Video via MLS: Toronto FC 0-0 Orlando City
Orlando City are in jeopardy of missing the playoffs after failing to score against a Toronto side reduced to 10 men in the second half.