49ers quarterback Jimmy Garoppolo led a five-game winning streak to end last season. (Kyle Terada/USA Today Sports)

SANTA CLARA, Calif. — For the first 11 games of their 2017 season, the San Francisco 49ers were one of the NFL’s worst teams. They won just once and seemed destined to land a top-five pick in the draft for a second consecutive season.

But then Jimmy Garoppolo, who had arrived from the New England Patriots in a trade a few weeks earlier, was inserted into the starting lineup. Suddenly, the 49ers looked like a completely different outfit. They closed the season with five straight victories, including knocking off a pair of playoff teams — Jacksonville Jaguars and Tennessee Titans.

It was a stretch that sent the franchise into the offseason riding high — and sent expectations for the future, both locally and nationally, soaring even higher.

“Jimmy Garoppolo will be one of the best trades the San Francisco 49ers have ever made as an organization in their history, in terms of the value they gave up,” ESPN’s Louis Riddick said on a conference call Friday. “I think he’s going to be fantastic.”

With Garoppolo in the fold, the 49ers are no longer viewed as a team plodding through a long-term rebuild under General Manager John Lynch and Coach Kyle Shanahan. Instead, they are seen as a team that can compete now, led by one of the league’s most compelling rising stars. From April to mid-June, Garoppolo’s jersey was the second-biggest seller in the league.

All of the excitement, however, clouds an important reality: This is a franchise that went 6-10 last season, not 10-6. And of those five season-ending victories, one — the finale against the Los Angeles Rams — came against a team that was resting for the playoffs, and two others — wins over the Chicago Bears and Titans — required last-second comebacks.

The schedule to begin the season is daunting, too. The 49ers open with one of the most anticipated matchups of Week 1 — a visit to Minnesota for Kirk Cousins’s Vikings debut — as part of a six-game stretch that features four road contests. All six opponents had .500 or better records last season. That’s a rough start for a team competing in a competitive division that includes a Super Bowl contender in the Rams.

All of that underscores a big question: Despite the hype surrounding Garoppolo’s rise, just how good will these 49ers be?

“Are we a perfect roster? No, we’re not there yet,” said Lynch, sitting behind a desk in his office inside the franchise’s gleaming practice facility, overlooking a pair of perfectly manicured fields. “We’ve blown this thing up in two years, and tried to recreate it. It’s probably gone faster than we might have thought. We still have a ways to go.

“But I do believe in us. I really do.”

In the NFL, where teams go from worst to first in a way they rarely do in other sports leagues, belief can go a long way — especially when it comes in the form of promising play at quarterback.

For the first time since the peak of the tenure of former coach Jim Harbaugh, when he and Colin Kaepernick had the 49ers within a play of winning a Super Bowl, there is a belief in these parts that the 49ers have a chance to do special things. And that is because of the golden arm of the new golden boy under center, on whom San Francisco has pinned its hopes of returning to the promised land.

“He’s not a scoreboard-type guy,” said Marquise Goodwin, one of Garoppolo’s top targets who caught 56 passes during a breakout season a year ago. “He’s just worried about the next play, and executing the opportunity we have in front of us.

“That’s what I love about him. He’s never negative. He’s always positive.”

Those positive feelings extend throughout the franchise, as the 49ers have not only backed their rising star by giving him a gigantic contract — a five-year deal worth $137.5 million — during the offseason, but also by making a variety of moves to bolster the talent around him. By extending Goodwin and left guard Laken Tomlinson, signing a new starting running back in Jerick McKinnon (who was lost for the season Saturday with a torn anterior cruciate ligament) and center in Weston Richburg, and using the ninth pick in the draft to take Notre Dame lineman Mike McGlinchey, who appears set to be the team’s starting right tackle, the Niners have placed a priority in building up Garoppolo’s supporting cast.

“We tried to complement his skills with talent around him,” Lynch said. “Those [moves] were all an effort just to surround Jimmy with talent that we think would be a great combo.”

The combination of Garoppolo’s talent and the play-calling of Shanahan, who is considered one of the league’s leading offensive minds, should allow San Francisco to put a lot of points on the board this season — even though Lynch cited the 49ers’ inability to finish drives during the preseason as something that needs to change when the real games begin.

But San Francisco’s playoff hopes will rest on what happens on the other side of the ball. Last season, San Francisco ranked 25th in scoring defense, 24th in yards allowed, tied for 26th in sacks and tied for 24th in interceptions. If the 49ers are going to take a step forward, it’s going to be because there is enough improvement defensively — particularly in one key area.

“On defense, they have to be able to rush the passer,” Riddick said. “Who is the guy on third down who can change the game for you, who can get the defense off the field and get that offense back on the field? I don’t know who that is going to be. And if they don’t have it … some of the deficiencies in the secondary, specifically on the corner, are going to be exposed.”

No one is more aware of that than Lynch, who spent 15 seasons as a star safety for the Tampa Bay Buccaneers and Denver Broncos. And, like Riddick, when asked for something he was concerned about on the team heading into the season, he pointed at San Francisco’s ability — or, in many cases, inability — to get to the quarterback.

“Can you disrupt the quarterback? That’s the key,” Lynch said. “The other thing I’ve seen on great defenses is you finish [the play]. That’s how you rule a game.

“When I was first in Tampa, it was, ‘Get the ball back for the offense.’ Then it became, ‘Let’s score.’ That’s your mentality. I’d like to see us take that jump.”

Given where the 49ers were last season, Lynch will likely settle for average play from his defense for now. And, if San Francisco can get that, it might be good enough to fulfill some of the hopes and dreams that have been placed upon the franchise after Garoppolo’s arrival and instant success last season.

“This is a team that’s exciting,” Riddick said. “They’re going to need some help. They’re going to need some breaks. They’re going to need some teams to underperform a little bit, and they’re going to have to overperform, because they still need some help.

“But I like their chances.”

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