Luis Diaz sat down at Hadlock Field, pencil in hand, clipboard in front of him, doing what most minor league starting pitchers do on their off days – charting pitches in the game.

When the Binghamton Mets took an 11-2 lead in the sixth inning, Diaz still kept track of Saturday’s pitches. But he began to think about Sunday’s pitches, the ones he would throw.

Sporting a black T-shirt with the slogan “Unleash the Beast,” Diaz was running the game plan through his mind.

“They can be free swinging,” he said. “Got to throw the first pitch for a strike, get ahead, and then mix in my change-up and curveball.”

Sunday is a do-or-die game after Saturday’s 11-4 loss to Binghamton in the Eastern League division series. The Mets and Sea Dogs are tied 2-2 in the best-of-five series.

While Diaz would have liked his teammates to wrap up the series Saturday, he was looking forward to the big-game feel of Sunday.

“I like it,” Diaz said. “I like it because of the adrenaline. This is THE game.”

This is the fifth time in franchise history the Sea Dogs have played a deciding Game 5. They have yet to lose one.

Their last Game 5 victory was memorable, coming at Hadlock Field in 2006 against the Akron Aeros for the Eastern League championship.

All the other Game 5 wins were in the division series.

Diaz, 22, a right-hander from Venezuela, has playoff experience. He pitched in Class A Salem’s opening game in the Carolina League playoffs last year and threw eight shutout innings.

“I think he’ll go out there and keep us in the game,” catcher Michael Brenly said. “When he has real good success, he establishes his heater. He’s got a fastball that can run up there in the 90s.

“When he established that, it makes everything so much better.”

But Diaz also has to have his curveball and change-up working.

Diaz arrived in Portland from Salem on June 18. In his first four starts, he was 3-1 with a 2.00 ERA.

Since then, he’s winless with a 5.81 ERA.

“I got in trouble trying to get my change-up over,” he said. “Sometimes I just threw fastball and curveball because I couldn’t throw my change-up for a strike.”

Diaz showed improvement in his last two start, allowing one earned run over 11 innings.

That has the Sea Dogs hopeful.

“He’s going to give us a chance to win. I’m excited,” said designated hitter Dave Chester, who was also on Salem’s championship team last year.

Chester has hit two home runs in this series, each coming in a loss. And while Saturday’s defeat was a rout, last Wednesday’s loss in Game 1 hurt more, as the Sea Dogs blew a 5-1 lead.

“We just have to come back (Sunday) and play our game,” Chester said. “We’ve been here before. That first game was way tougher than (Saturday), and I thought we bounced back well.

“Hopefully we can do it again (Sunday).”

Diaz has faced Binghamton twice, going 0-1 with a 4.96 ERA. His most recent start against the Mets was July 22, when he gave three runs in seven innings.

Diaz will likely be followed by some of Portland’s best relievers. Wilfredo Boscan (3.88 ERA) has pitched 12 straight scoreless innings, including three against Binghamton on Thursday. With Noe Ramirez now in Pawtucket, Robby Scott (1.96) may assume the closer role.

Binghamton will strut out an impressive starter. Gabriel Ynoa (3-2, 4.21) is ranked as the Mets’ No. 15 prospect by Baseball America. Ynoa, 21, has faced Portland twice (1-0, 1.42 ERA).

Diaz vs. Ynoa. Sea Dogs vs. Mets. Game 5.

“I’ll do what I have to do,” Diaz said.