Welcome back, 49ers fans.

It has been a minute.

Plenty of the, ahem, Faithful checked out last year after the loss of injured quarterback Jimmy Garoppolo foreshadowed the brutal and boring season to come.

Now it’s time to tune back in while saying goodbye to that four-win slog.

The 2019 league year opens at 1 p.m. Wednesday with the start of free agency, which will signal the shift from bemoaning losses to, quite possibly, celebrating big-name gains.

The 49ers will enter free agency with the NFL’s sixth-most salary-cap space, just more than $66 million, a host of needs and a sense of urgency that has been lacking during the first two years of a patient “brick-by-brick” rebuild that has featured 10 wins in 32 games.

The 49ers and other teams can begin negotiating Monday with agents during the “legal tampering” period, but contracts can’t be signed until Wednesday.

In 2017, the 6-10 season was excused because general manager John Lynch and head coach Kyle Shanahan inherited a 2-14 mess. And last year’s mess was forgiven largely because their franchise quarterback was lost in Week 3.

Both Lynch and Shanahan subtly have acknowledged that 2019 has a different vibe.

At the recent NFL combine, Shanahan acknowledged this offseason is a “very pivotal time for us” and Lynch noted players who have viewed the 49ers as an attractive destination under the new regime could adopt a different view.

“I think we all know the reality that to keep that feeling,” Lynch said, “we better start winning some football games on a consistent basis.”

The 49ers’ power duo also noted the need for “difference-makers” and “closers.” And the Niners likely will try to address their lack of impact players on defense a year after their two biggest free-agent splurges, center Weston Richburg and running back Jerick McKinnon, were on offense.

Last year, the 49ers were historically bereft of big plays on defense. They had seven takeaways, shattering the record the fewest in NFL history, and their two interceptions also established a league record. Part of the issue was their inability to force quarterbacks into mistakes with pass-rush pressure.

Their much-discussed search for a strong edge rusher could net results this week.

On Sunday, Kansas City released Justin Houston, a four-time Pro Bowl selection who ranks ninth among active players in career sacks (78.5). In addition, the 49ers also reportedly have been in contact with Kansas City about trading for franchise-tagged Pro Bowl pass-rusher Dee Ford.

The free-agent market also includes New England’s Trey Flowers, Detroit’s Ziggy Ansah and Washington’s Preston Smith. On Sunday, the Rams’ Dante Fowler, about whom the 49ers inquired at last year’s trade deadline, re-signed with Los Angeles.

As for their secondary, it wouldn’t be a surprise if the 49ers made an aggressive run at Seattle free safety Earl Thomas, 29, a six-time Pro Bowl selection who ranks third among active safeties in interceptions (28). In 2018, Thomas had more interceptions (three) in four starts than the 49ers managed in 16 games.

The 49ers have pursued players who rank among the best at their positions. Last year, they signed cornerback Richard Sherman, tried to trade for Raiders-then-Bears pass-rusher Khalil Mack and reportedly considered dealing for Giants wide receiver Odell Beckham Jr.

Despite sustaining a broken left leg in two of the past three seasons, Thomas remains arguably the NFL’s top free safety. And he’d like his salary to reflect that status. Thomas is seeking to surpass Kansas City’s Eric Berry ($13 million average) as the league’s highest-paid at his position. Thomas is seeking at least $15 million.

Thomas is the top prize, but other free-safety options include Houston’s Tyrann Mathieu, Washington’s Ha Ha Clinton-Dix and the Rams’ Lamarcus Joyner.

A lesser-priced option could allow the 49ers to make a run at Baltimore inside linebacker C.J. Mosley, who will command a huge contract, given his youth (26) and four Pro Bowl selections in his first five seasons.

The 49ers need a player to pair with inside linebacker Fred Warner after they, in effect, wasted a first-round pick in 2017 on Reuben Foster, who was released in November.

Shanahan has noted teams are required to “overpay” for players in free agency and the 49ers would prefer to strategically supplement their roster by signing players while building with draft picks.

Still, they have plenty of money and urgency this week.

So, welcome back and stay tuned: It should be more exciting than their 2018 season.

Eric Branch is a San Francisco Chronicle staff writer. Email: ebranch@sfchronicle.com Twitter: @Eric_Branch