The Cardinals were up 20-0 over the Giants at halftime and then had a 28-7 lead early in the third quarter.
But they were outscored 24-0 the rest of the way to fall 31-28 in regulation.
With such a dramatic collapse, head coach Jonathan Gannon took the blame for the loss.
“They had a couple of drives there that were long and the guys with the defensive side, that starts with me,” Gannon said in his postgame press conference. “Exactly what we couldn't do to lose that game coming out of halftime we did and when that is the case that's on me explicitly.”
Gannon, who was previously the Eagles defensive coordinator, also took the blame for the defense not containing New York’s Daniel Jones — who made plenty of plays with his legs.
“It fell solely on me with that,” Gannon said. “We've got to understand a little bit better and execute a little bit better. It starts with me."
The Cardinals are now 0-2 with losses to the Commanders and Giants. Things won’t get easier next week, as Arizona continues its tour of the NFC East with a matchup against the Cowboys.
"We've got to coach better,” Gannon said. “We got outplayed in the second half. A tale of two halves. We have to do a better job to help our guys out because the effort's there and the intensity is there — we've got to coach a little bit better."