Lately, Don Mattingly has been cajoling Tino Martinez to be more aggressive. Well, it doesn’t get any more aggressive than swinging at a 3- and-0 pitch.

The suddenly scintillating Martinez was given the green light in a critical eighth-inning situation yesterday, and he smashed a three-run homer to seal a 6-0 victory over Oakland.

It was Martinez’s fourth homer in his last 15 at-bats – and the first of those in which he had a three-balls, no-strikes advantage.

“I felt good at the plate. If I didn’t feel good, I would’ve taken it and let Jorge (Posada) do it,” Martinez said.

Actually, Posada followed Martinez’s huge blow with a solo shot, the first time this season Yankee teammates have hit back-to-back jacks.

The four-run eighth allowed closer Mariano Rivera to get another breather after Friday’s 50-pitch blowup.

It gave the rest of the Yanks an opportunity to exhale after only leading 2-0 heading into the inning.

“Sure, you want to give Mo some rest if he needs it,” Martinez said. “Hopefully we would get one or two runs there, make it at least a three- or four-run lead.

“That worked out well.”

Martinez was the No. 8 hitter as recently as Thursday but took sixth in the order yesterday. His shot off righty reliever Kiko Calero carried just over the fence into the first row of the rightfield seats.

“When it first left the bat, I said, ‘We got a run,’ ” manager Joe Torre said. “And then I realized he pulled it a little more than I thought he did.”

Said Martinez: “Just looking for a ball inside, something to drive. I didn’t really kill it, but I thought I hit it good enough to get out.”

Interestingly, Martinez looked every bit his age (37) when Oakland starter Rich Harden blew two fastballs by him in his first two at-bats.

One was 98 mph, one was 96 mph, and both were well above the belt.

“He was really angry with himself early on,” Torre said. “He was swinging at some bad balls. He was kicking himself in the rear end.”

Torre revealed Mattingly’s recent instructions to Martinez, while the vet credited his hitting coach for all the work they’ve done this season.

Martinez’s sixth of the year – and second in two games – seemed like sweet redemption after he chucked away Friday’s game in the 10th inning, but he said there’s a lot of work left.

“We want to come out every night with that same intensity and keep pushing forward and not really be satisfied,” he said. “Two games is two games.

“We’re looking for consistency over months at a time.”