SANTA CLARA, Calif. – The Giants were faced with a daunting collection of circumstances Thursday night in Levi's Stadium.

They played their second game in five days on the west coast. Their opponents had the NFL's longest regular season winning streak at 12 games and were playing their home opener after two victories on the road. Two of the Giants' very best players were not in uniform because of injuries. They started their third different offensive line configuration in the young season.

Even the day and time conspired against them. The Giants had lost seven consecutive games on Thursday and 13 of their last 14 prime time games.

Despite those factors and sizeable statistical disadvantages, the Giants had a chance to pull within three points in the third quarter. But the San Francisco 49ers scored the game's final 13 points to defeat the Giants, 30-12. The Giants, who won in Arizona last Sunday, are 1-2.

"We're not going to make excuses about any of it," coach Brian Daboll said.

"We didn't create a rhythm," quarterback Daniel Jones said. "We didn't execute, didn't take advantage of our opportunities. Certainly, it is a good defense. It's a good team. When you're playing good teams, you can't afford to do that. We didn't play well enough."

The numbers confirm that. The Giants had far fewer total yards (441-150), rushing yards (141-29) and first downs (26-10) and owned the ball for only 20:50.

The Giants played without Pro Bowl running back Saquon Barkley (sprained ankle); All-Pro left tackle Andrew Thomas, who missed his second straight game with a hamstring injury; and left guard Ben Bredeson (concussion). Joshua Ezeudu and Shane Lemieux started on the left side of the O-line and Matt Breida replaced Barkley.

Jones completed 22 of 32 passes, but for only 137 yards. Breida rushed for 17 yards. The Giants' receiving yardage leader was Darius Slayton with 32. The Giants failed to secure some passes that should have been caught, including one that tight end Darren Waller couldn't corral and was intercepted by Talanoa Hufanga.

"I gotta help out as a teammate and make that play, wherever the ball's placed," Waller said. "So yeah, I felt like it's something I gotta bring in. … Anytime your hands get on it, you gotta make it."

"Whenever it's not going (well), or you feel like you have these opportunities and you miss out of them, it's always frustrating," Breida said. "But you gotta move on to the next play and we'll be a better team from this."

The 49ers demonstrated why they have played in the last two NFC championship games and are among the favorites to get there again.

Second-year quarterback Brock Purdy improved to 10-0 when he starts and finishes a game and threw for 310 yards and two touchdowns, a nine-yarder to Ronnie Bell and a 27-yarder to Deebo Samuel (129 yards on just six catches). Christian McCaffrey rushed for 85 yards and a touchdown and added 34 yards on five receptions. The 49ers converted nine of 16 third-down opportunities (56.3%).

"That's a heck of a team," Daboll said. "It usually comes down to making plays when you have an opportunity to make plays. They did a good job, give them credit."

Particularly galling to the Giants was San Francisco's success on third down.

"We didn't execute, we didn't tackle, that's just it," cornerback Adoree' Jackson said. "We had them in third and long situations, we were winning first and second down, and we just didn't tackle and execute."

The 49ers seized control of the game in the first half, when they scored 17 points on scoring drives of 15, 11 and 11 plays. Rookie kicker Jake Moody and Giants veteran Graham Gano kicked first possession field goals and the first quarter ended deadlocked at 3-3.

The game began to get out of hand early in the second quarter when a pass to Samuel gained 30 yards on third-and-15 and Purdy's pass to McCaffrey picked up 17 on thrd-and-13. Those conversions set up Purdy's nine-yard touchdown pass to Bell.

"I think they were seven of nine in the first half (actually 7 of 10)," Daboll said. "And a few of them were screens where they just caught and run. We've got to rally the ball out and make tackles. Third down was huge tonight in this game. It was a contributing factor to doubling the time of possession on both sides. When you're not converting third downs and you're giving up some third downs, there's time of possession. Your defense gets tired and we're not out on the field offensively enough. It's a collective thing."

"They just outplayed us on third down and we have to do better with those screens, running to the ball and getting guys down," defensive lineman Dexter Lawrence said.

After the Giants went three-and-out, San Francisco drove 73 yards in 11 plays, the last McCaffrey's four-yard touchdown run up the middle.

Gano concluded the first-half scoring with a franchise record-tying 57-yard field goal to lift the Giants to within 7-6 at halftime.

Early in the third quarter, Shemar Jean-Charles was penalized for interfering with Eric Gray's fair catch attempt on a punt, giving the Giants possession at San Francisco's 37-yard line. A 22-yard pass interference penalty on Deommodore Lenoir helped move the ball to the eight and from there, Breida bulled his way into the end zone. That made it 17-12, but Jones was sacked on the two-point conversion try and the Giants never got closer.

"We came back out in the second half, had a score, went for two to try to cut it to three," Daboll said. "Just give them credit. They did a lot of good stuff. That's a good team."

The Niners tacked on 13 points on two Moody field goals and Samuel's fourth quarter touchdown catch.

In their locker room after, the Giants found some positives to take from the game.

"I think it was frustrating at times, but I felt like we were in the game really until the end and had chances to make plays really until the end," Jones said. "I think we stayed confident and believed and we just didn't do it there down the stretch. I think we did a good job kind of keeping a level head and competing."

"I think it just shows the heart that we have and the competitive stamina that we have as a unit," Lawrence said. "I think we just got to keep going out there and fighting and showing who we are."