He said the hard work was done by the pass rush that made Philadelphia's Sam Bradford hurry the throw and the tight coverage of the cornerbacks that forced the ball to the middle of the field.
''They tipped the ball and it landed in my lap,'' Allen said.
Atlanta recovered after blowing a big halftime lead and beat the Philadelphia Eagles 26-24 on Monday night to give new coach Dan Quinn a dramatic win in his debut.
Matt Bryant kicked four field goals, including a 47-yarder with 6:27 remaining that gave the Falcons the two-point lead. There seemed to be little chance that small lead could withstand another possession by the Eagles.
The Eagles, who fell behind 20-3 at halftime, seemed unstoppable in the second half. DeMarco Murray had an 8-yard scoring run and a 5-yard touchdown catch in the third quarter. Ryan Mathews' 1-yard scoring run gave the Eagles a 24-23 lead midway through the final period.
Following Bryant's 47-yarder, Philadelphia's Cody Parkey was wide right on a 44-yarder.
Matt Bosher's 57-yard punt left Bradford with 1:49 remaining as he started a final drive at the Eagles 14. Bradford completed one short pass, followed by an incompletion, before his third-down attempt when through Jordan Matthews' hands - straight into Allen's grasp.
As Matthews went down to his knees, his head to the turf, the Falcons began their celebration.
''I've just got to make a play, nothing more, nothing less,'' Matthews said.
Bradford, making his debut for the Eagles and his return from two knee surgeries, was 36 of 52 for 336 yards with one touchdown and two interceptions.
Some observations from the Falcons-Eagles opener:
RYAN'S RECOVERY: Falcons quarterback Matt Ryan shook off a pair of interceptions, including one on the first possession of the second half that turned the momentum in Philadelphia's favor. He was 23 of 34 for 298 yards, including touchdown passes of 4 and 22 yards to Julio Jones, who had nine catches for 141 yards.
RUN GAME WOES: Murray, who opened the 2014 season with eight straight 100-yard games for Dallas, found less room to run in his debut with the Eagles. After leading the NFL with more than 1,800 yards rushing last season, Murray was held to 9 yards on eight carries. He had minus-4 yards on four carries in the first half.
Darren Sproles, who often looked too quick for the Falcons' defense, had 50 yards rushing. Ryan Mathews had only 4 yards.
SLOW START: The Eagles' first four possessions ended with punts. They were held to six first downs and eight yards rushing in the half.
''I felt like we were behind the sticks all day,'' Bradford said. ''It seemed like we couldn't get anything going on first down, which put us in second and long, third and really long.''
COLEMAN-FREEMAN COMBO: As expected, Falcons rookie Tevin Coleman started at running back and was effective with 20 carries for 80 yards. After missing all four preseason games with a hamstring injury, Devonta Freeman added 10 carries for 18 yards and three catches for 29 yards.
''Bad read, bad throw,'' Bradford said. ''It's just one of those things that can't happen. ... You have to be careful with the ball when you are backed up.''
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