MacMath had a strong game from the beginning to the end, saving Dax McCarty's point-blank header in injury time inches from the goal line.
Philadelphia (10-7-8) came close to giving up a winning goal in the 63rd minute, but was bailed out when MacMath leaped in front of Peguy Luyindula and grabbed Tim Cahill's header near the goalmouth. MacMath made two huge saves in the first half as well. He shares the MLS lead for clean sheets (9).
The draw moved New York (11-8-6) into a tie for first in the Eastern Conference with Sporting KC. The Union are a point back in third with 38 points.
The Red Bulls had the better of the action, especially in the second half as the Union failed to exert significant pressure except for two good opportunities by Sebastian LeToux. The midfielder blasted a shot in the 73rd minute that clanged off the crossbar, and had a point-blank chance in the 80th minute that Luis Robles stopped with a fingertip save.
Jonny Steele nearly put the Red Bulls on the board in the 79th minute with a shot was just wide of the right post.
The Red Bulls had the best chance of a scoreless opening half on Fabian Espindola's header off a feed from Jonny Steele in the 34th minute. But MacMath got his hand on it and lifted it over the crossbar.
MacMath saved the Union in the 29th minute, too, when he came out in front of Thierry Henry to grab McCarty's cross, thwarting what would have been an easy header for the Red Bulls' captain and scoring leader.
Defense marked the half, especially in the midfield where space for both teams came at a premium. The tight marking deprived New York and Philadelphia of any chance at a breakaway, and the play of the back fours kept the teams from converting the feeds from the wings.
Still, the Red Bulls managed to outshoot Philadelphia 7-2. Espindola and Henry had two shots each for the Red Bulls. Casey had both the Union's shots.