SANTA CLARA, Calif. — Offensive coordinator Mike Martz revealed why he called a running play for the fullback on the final play of the game Monday night: He mistakenly thought the play began at the half-yard line.

"We did not know the ball was going to be on the 3 1/2 (yard line), obviously, or we would have never called that play," Martz said of the hectic and confusing final seconds of the 49ers' 29-24 loss to Arizona.

That confusion apparently lasted into Tuesday. The final play, on which Michael Robinson was held to a 1-yard gain, began at the 2-1/2-yard line, not the 3 1/2.

Martz left the stadium and went to bed thinking that the play had been from a shorter distance. What is more bizarre is that the person who ultimately clarified for him what transpired was former head coach Mike Nolan, who was fired by the 49ers three weeks ago. Martz said Nolan called him Tuesday morning.

"He was the only one that was smart enough to look at the TV, and he knew immediately," Martz said. "He's the only one that really knows football well enough to know exactly what happened."

What Nolan explained was how the 49ers lost yardage when officials reviewed Frank Gore's second-down run, the penultimate play of the game. Officials originally marked Gore down at the 1 1/2 yard line.

The play was reviewed to see whether Gore was touched down by an Arizona defender or whether he crossed the goal line before being touched. If the play wasn't a touchdown, the 49ers figured, they'd at least have the ball somewhere inside the 1 yard line.

At that point, the play was radioed-in for Robinson.

When the officials reviewed the play, however, they determined that Gore was touched down at the 2 1/2 and moved the ball accordingly. They did not explain to the 49ers coaches that they were doing so.

"There was a lot of confusion at the end," Martz said. "The only thing I wish had happened — and the officials always do this — the officials come over and explain to you what's going to happen based on what they saw on the replay. And for whatever reason they neglected to do that. That's a courtesy that's always afforded. Why they didn't do that, I don't know."

While millions watching on television knew what was happening courtesy of the referee's microphone, Martz said the explanation was drowned out by the crowd noise.

"Nobody on the sideline can hear the official over the speaker," Martz said.

Asked why no one from the coaches' booth informed him of the true position of the ball, Martz said that the connection between the sideline and the quarterback cut off before they could change a play. That is, by the time coaches realized what was happening, it was too late.

"All things considered, if they had moved it back to the 10-yard line, we couldn't have changed the play," Martz said. "It wouldn't have mattered."

Both Martz and interim head coach Mike Singletary took blame for another end-of-game mistake — allowing more than 20 seconds to tick off the clock between receiver Jason Hill's 14-yard reception to the 1 1/2 yard line and quarterback Shaun Hill's spike of the ball, which left 20 seconds.

The 49ers had two personnel groups on the field, and Hill couldn't have snapped the ball without incurring a penalty.

"That's on me," Singletary said. "That is my job to make sure that whatever is wrong that it gets done and it gets done in the right fashion. ... So, I will put on the jacket for that. I will wear it, we will fix it and will go from there."

Martz later said he was in too much of a hurry to get the new personnel group — the "tank group" for a goal-line plunge — onto the field and should have spiked the ball first.

"That's just a bad job of coaching on my part," he said. "I knew what I wanted to do. I called out two different things at the same time."