New York Giants defensive end Osi Umenyiora, who won’t play against the Redskins after undergoing arthroscopic knee surgery, is one of many defensive players who will sit out the game. (Julio Cortez/Associated Press)

The list of injuries has grown so long for the New York Giants in recent weeks that they find themselves answering many more questions about ominous signs than hopeful developments as they prepare for Sunday’s season opener against the Washington Redskins at FedEx Field.

But the dawn of a new season is supposed to be about optimism, and the Giants were doing their best last week to remain upbeat even as the injury-related news grew worse.

“It’s unfortunate,” Coach Tom Coughlin said at midweek. “There’s no question there’s a number of defensive players that we were counting on that are not going to be with us. . . . But still, we have what we have and we’re going forward with it.”

The Giants have had a habit in recent years of stockpiling productive pass-rushers, but they could be short-handed even in that area Sunday. One of their standout defensive ends, Osi Umenyiora, will be sidelined against the Redskins after undergoing arthroscopic knee surgery. The other, Justin Tuck, missed practice time last week with a neck injury that puts his status for the opener in doubt. The Giants have second-year pro Jason Pierre-Paul, who had 41 / 2 sacks last season as a rookie, to fill in at one defensive end spot, but the Redskins could catch a break if Tuck is sidelined or limited.

All of that comes after a preseason filled with injuries to Giants cornerbacks. They lost projected starter Terrell Thomas to a season-ending torn knee ligament and prized rookie Prince Amukamara to a broken foot. Amukamara, a first-round draft choice in April, was hurt in his second practice of training camp and will be sidelined until at least late this month.

On Tuesday, Coughlin and his staff learned that Jonathan Goff, the team’s starter at middle linebacker and defensive signal-caller, had torn an anterior cruciate ligament in his right knee during a practice-field collision Monday. Goff is out for the season, replaced by rookie Greg Jones, a sixth-round draft pick out of Michigan State.

“It’s definitely unfortunate that we lost some of the guys that we lost — Goff, Terrell,” said Giants safety Kenny Phillips. “They were a big part of what we do on defense. But that has given some opportunities to some other guys to step in there.”

Quarterback Eli Manning is scheduled to make his 104th straight regular season start Sunday. That becomes the longest active streak among NFL quarterbacks, with his older brother Peyton missing from the Indianapolis Colts’ lineup for the first time in 14 seasons.

The Giants praise Manning’s reliability and productivity. He threw for 4,002 yards and 31 touchdowns last season. But he also threw 25 interceptions, the most in his seven-year NFL career.

“We’ve got to be smart with the football,” Manning said at midweek. “We have to protect it. If we have an opportunity to make some big plays, we have to make those. We’ve just got to be sound.”

Manning is playing behind a partially remade offensive line, after the Giants released veteran center Shaun O’Hara and guard Rich Seubert following the lockout. Many in the league assumed the Giants would re-sign wide receiver Steve Smith. Instead, he went to the rival Philadelphia Eagles as part of their post-lockout shopping spree.

The Giants explored the possibility of re-signing wide receiver Plaxico Burress after the former Super Bowl standout served nearly two years in prison on a weapon charge. But Burress ended up with the New York Jets. A training-camp contract dispute between Umenyiora and the Giants also generated headlines before his knee surgery.

After the Giants learned the details of Goff’s knee injury Tuesday, the dark clouds that hovered over their training facility Wednesday seemed fitting. But Coughlin spoke of his excitement for the season, and players said that day’s practice had gone well.

Coughlin was asked if he was shaking his head about the run of injuries.

“I don’t put it that way,” he said. “But you do have your moments. I mean, we are human. . . . But hey, nevertheless, press on. That’s what we’re charged with. So here we are.”

The Giants are trying to get back to the playoffs after going 10-6 last season but missing the postseason for a second year in a row.

“We’re not worried. . . . The only thing we should be worried about is what we have to do to the next team we play,” safety Deon Grant said. “But as far as being worried about a guy on the football field with us, our confidence level better be very high . . . when it comes to believing in whatever guy’s lined up in front of us, behind us, beside us.”