New York 1-2 New England
Jermaine Jones gave New England a crucial advantage in the chase for the MLS Cup as his late winner left the New York Red Bulls to regret a host of wasted opportunities.
Teal Bunbury had given the visitors a 17th-minute lead at the Red Bull Arena in New Jersey, but Bradley Wright-Phillips levelled 10 minutes later.
However, the New York striker and his team-mates were guilty of missing a number of chances to win the match before Jones slotted home an 85th-minute winner.
To add insult to injury, Wright-Phillips received a foolish yellow card for needlessly blocking New England goalkeeper Bobby Shuttleworth and will now miss the second leg at the Gillette Arena next weekend.
Jones almost gave the Revolution a fourth-minute lead with a powerful close-range header, but Luis Robles was able to palm the ball away.
At the other end of the field, Lloyd Sam broke clear and forced a good save from New England goalkeeper Shuttleworth.
Wright-Phillips was looking for a 16th-minute penalty, but Kelyn Rowe's challenge on the New York striker was deemed legal.
One minute later, though, New England went ahead. A Jones run to the right allowed Bunbury to pick up the ball, and he cut inside before curling a sweet strike beyond Robles.
A.J. Soares became the game's first caution for a foul on Wright-Phillips in the 23rd minute, but Henry's subsequent free-kick came to nothing.
Jones followed his team-mate into the referee's notebook three minutes later after an illegal challenge on Dax McCarty.
Moments later, New York were level. Peguy Luyindula broke forward and saw one shot blocked by Shuttleworth before hooking a second chance against the crossbar. But Wright-Phillips was alert to the loose ball and headed home the equaliser.
A superb ball over the top from Luyindula almost set up Wright-Phillips for a second New York goal, and Ibrahim Sekagya picked up a yellow card for a foul.
Wright-Phillips squandered a great chance to give New York the lead in first-half injury time when he headed over from close range after a great cross from Henry.
Scott Caldwell got himself into a dangerous position early in the second period but chose to play the ball wide with no team-mate arriving when he could have shot at goal.
Henry unleashed a 51st-minute drive at goal which Shuttleworth could only spill into the path of Sam, but the New York man could only fire the rebound into the side netting.
Wright-Phillips spurned another opportunity in the 59th minute after being played through by a clever Sam ball, but the New York forward's shot was straight at Shuttleworth, who pushed the effort away.
Shuttleworth was again the hero for New England when he blocked a McCarty close-range header from a Henry corner.
In the aftermath of that incident, Wright-Phillips was cautioned for blocking Shuttleworth's clearance, meaning he will miss the second leg of the semi-final next weekend.
An injury to Rowe forced New England into a change just after the hour mark, with Kevin Alston coming on to replace his team-mate.
New England missed their own glaring chance in the 72nd minute when Davies failed to get a foot to a cross from the right before Jones headed over the loose ball from just inches out.
New York brought on Tim Cahill for Eric Alexander in a bid to chase a first-leg win to take into the return game. Within seconds of entering the game, the former Everton forward was booked for a foul on Jones.
Jones was gifted a chance on goal by a poor Richard Eckersley header, but the USMNT international could not get the ball from out of his feet to set up a clear shot on goal.
Lee Nguyen joined the names in the notebook before Henry attempted to find Cahill with a chipped free-kick from distance.
With five minutes remaining, Nguyen broke clear and found Bunbury free to his right. Unselfishly, the first goalscorer crossed for Jones, who was arguably offside, to slot home.
New England will now go into the second leg as favourites to reach the MLS Cup final on Dec. 7, while New York must regroup after a disappointing home defeat.
Selected Player Ratings
Thierry Henry: B+
It was a low-key opening period for the former Arsenal and Barcelona striker, but he played his part in the equaliser.
Jermaine Jones: A
Jones was always busy in the first 45 minutes and played the key ball for Bunbury's opening goal. And his late winner was just reward for his performance.
Bradley Wright-Phillips: A-
Wright-Phillips was swift to see the possibilities to level the scores for New York in the opening half of the game. But he missed a glut of chances to give New York a decent lead before earning an unnecessary booking to rule himself out of the second leg.
Both clubs are next in action on Saturday in the second leg of the semi-final at the Gillette Stadium in Boston.