The Giants managed to win despite making just nine first downs and punting eight times.
Hoping to end their trend of missing the playoffs a year after reaching the Super Bowl, the Giants (6-7) snapped a three-game losing streak. But they still but trail Tampa Bay and New Orleans by 1 1/2 games for the final NFC wild card spot.
"We didn't play the way we should have and I was disappointed in a lot of things," Giants coach Jim Fassel said. "We had a lot of drops out there and I don't know what that was all about, but we fought back in the end."
The loss virtually eliminated the Cardinals (5-8) from the postseason race.
"I'm extremely sick for those players in there because they put everything they had out there and we didn't get it done," Cardinals coach Dave McGinnis said. "In a game this close there are a lot of what-ifs, but the only what-if that matters is you have to win at the end and we didn't get that done today."
Arizona took a 13-10 lead when tight end Tywan Mitchell made a leaping 24-yard touchdown catch over Giants cornerback Jason Sehorn in the back of the end zone on fourth down with 4:04 left in the fourth quarter. Sehorn appeared to be in perfect position to knock the pass down, but let the ball go through his hands and Mitchell was able to make a leaping catch and keep both feet inbounds.
But after faltering most of the day on offense, the Giants marched 70 yards in 11 plays for the winning score. Running back Tiki Barber kept the drive alive with an 11-yard catch on third and 10 to the Arizona four.
Two plays later, Toomer faked out rookie cornerback Renaldo Hill by sprinting towards the back of the end zone and then suddenly stopping to easily catch the winning touchdown pass from Kerry Collins.
"It's a play we work on a lot and I just try to run to the back of the end zone and Kerry put up a short ball and I just adjusted to it," Toomer said. "I think the defensive back (Hill) fell down, because I came at him at a good pace and put the brakes on and he just kept going."
Toomer had a series of drops and just one catch for 13 yards before New York's winning drive. After Ike Hilliard made a nine-yard catch on third and six to the Arizona 29, Toomer had a 14-yard reception on a slant over the middle.
Collins threw two incompletions, but his trusty safety valve Barber made a big play out of the backfield when he caught a short pass and bulled his way to the Arizona four.
"Tiki on third down made the big play when we needed it," said Collins, who had passed for just 91 yards before completing 6-of-9 for 56 yards on the winning drive.
Barber, who rushed for 118 yards in the Giants' 17-10 win at Arizona last month, had 85 yards on 16 carries and caught five passes for 35 yards.
The Cardinals held a huge advantage in time of possession, controlling the ball for nearly 37 minutes. But they managed just a pair of field goals by rookie Bill Gramatica before Mitchell's fourth-quarter touchdown catch.
Despite having the ball for more than 20 minutes in the first half, the Cards could not get into the end zone, settling for field goals of 42 and 23 yards by Gramatica. To make matters worse, Gramatica strained his right knee while celebrating his first field goal, forcing the Cards to use safety Pat Tillman on kickoffs.
After making his 42-yard field goal with 7:41 left in the first quarter, Gramatica leaped in the air to celebrate and winced in pain. When he landed, Gramatica fell to the ground and clutched his knee.
Gramatica kicked a 23-yard field goal with 13:33 left in the second quarter, but was in obvious pain, forcing the Cards to Tillman on kickoffs.
McGinnis expressed his frustration with Gramatica afterwards and called the injury the most bizarre he had ever seen.
"Disbelief. Disbelief," McGinnis said of Gramatica's injury. "It alters you some when you lose your kicker. I mean very much so because now we're playing a different field position game and I had to adjust and change our thinking as far as what we were going to do once we got into certain field position areas."
Ironically, Gramatica's injury actually benefited the Cardinals on their only touchdown drive of the game when they converted two fourth-down plays.
With the Giants leading, 10-6, Arizona was facing a fourth and nine at the New York 30 with 5:23 left. Instead of having the option of a field goal, the Cards went for a first down and Jake Plummer rolled right and drilled an 11-yard pass to Mitchell.
After two incompletions and a five-yard loss by Thomas Jones on a running play, the Cards had a fourth and 15 at the New York 24 with 4:20 left. Forced to go for the first down again, Plummer tossed a pass to the back of the end zone that Mitchell hauled in.
"That was a great catch, give Ty all the credit for that," said Plummer, who was 27 of 45 for 207 yards but was denied his fifth fourth-quarter comeback of the season. "We've been in every ballgame we've played and we just have to keep fighting."
Ron Dixon, who had just four receptions this season, caught a 26-yard touchdown pass with 5:06 left in the first quarter to cap a five-play, 70-yard drive for the Giants. New York managed a total of 101 yards on 43 plays in its other nine possessions before the winning touchdown drive.
Morten Andersen kicked a 39-yard field goal with 11:50 left in the fourth quarter for New York.
Arizona's David Boston, who had seven 100-yard games in his previous eight, had eight receptions for 84 yards. He has 86 receptions for a league-best 1,387 yards.
New York defensive end Michael Strahan had a half-sack, raising his league-leading total to 17. Mark Gastineau holds the single-season record with 22 sacks for the New York Jets in 1984.