For most of the last two decades, the Cleveland Cavaliers could be defined by two things: LeBron James or irrelevance.

James, a hometown hero, breathed new life into the city upon being drafted in 2003, and made the Cavaliers a must-see attraction. And then he devastated the fan base by leaving for Miami in 2010, before returning like Odysseus in 2014 and delivering one of the most storied championships in N.B.A. history in 2016. Two years later, he left again, leaving the franchise without a clear path forward.

“Everybody felt a little bit weirdafter that year,” said Cedi Osman, a fifth-year guard for Cleveland.

The Cavaliers were starting from scratch and staring into the abyss. They had past-their-prime veterans and no track record of luring top free agents. But a funny thing has happened. Fast forward through some quality draft picks, a savvy trade and a key player’s unexpected resurgence, and there is a basketball renaissance in Cleveland.

Four seasons after James’s exit to the Los Angeles Lakers, the Cavaliers have confounded expectations to become one of the best teams in the Eastern Conference with one of the best defenses in the N.B.A. For the first time since James left in 2018, the Cavaliers will be represented in the All-Star Game, which is this weekend in Cleveland. Rajon Rondo, the veteran point guard traded to Cleveland from the Lakers last month, said the Cavaliers this season have “a chance to do something special.”

Their status as a contender was cemented last week when they acquired Caris LeVert, a 27-year-old swingman and Ohio native, from the Indiana Pacers. LeVert told reporters the team seemed to have “such positive energy everywhere.”

Positive energy has been in short supply in recent years. Over the past three seasons, the Cavaliers went 60-159. The rebuilding process post-James, helmed by General Manager Koby Altman, has been bumpy.

Cleveland is on its fourth head coach in four years. One of them, John Beilein, apologized to his team of mostly Black players in 2020 for calling them “thugs” in a film session. He resigned later that year midseason with a dismal 14-40 record.

There was also the trade for Andre Drummond, a slow and expensive center who rebounded well but didn’t fit with the team’s quick perimeter guards, and the extension for another center, Larry Nance Jr., who never quite lived up to a contract worth more than $40 million.

“We’ve taken some time and had to be really patient through some difficult times to get to where we are,” Coach J.B. Bickerstaff, who replaced Beilein, said during a news conference last week. “And when you’re talking about legacy, I think those are discussions that you have after the season or, you know, two years from now when you can look back at a total body of work and see what you’ve truly done.”

The core for the Cavaliers’ resurgence has come through the draft. Point guard Darius Garland, selected with the fifth pick in 2019, was a highly-touted but risky pick given that he played in only five games at Vanderbilt because of a knee injury. The Cavaliers had drafted point guard Collin Sexton only the year before, which made the selection of Garland raise some eyebrows.

The team instead started Garland and Sexton as one of the more dynamic backcourts in the N.B.A. Now, in only his third year, the 22-year-old Garland is averaging 20.1 points and 8 assists per game as a deft floor general and earned an All-Star berth. (Sexton sustained a season-ending knee injury in early November.)

With his passing skills and ability to create space for himself in the paint, Garland has outplayed at least two players drafted ahead of him (RJ Barrett and De’Andre Hunter), while the No. 1 pick from that draft, Zion Williamson, hasn’t taken the floor this season because of a foot injury.

Brandon Knight, who was Garland’s teammate briefly during Garland’s rookie year in Cleveland, described him as “super, super, super unselfish.”

“He scores a lot, but he also gets a lot of guys involved,” Knight, 30, said. “When you get guys involved and you get guys feeling good about themselves and feeling good about touching the basketball, I think it trickles down.”

When a team isn’t traditionally attractive for free agents, hitting on high draft picks is crucial. Cleveland drafted Isaac Okoro fifth in 2020, and he has become a reliable defender and open-floor finisher. The draftee with the highest ceiling might be Evan Mobley, who was picked at No. 3 in last year’s draft. Mobley, 20, is averaging 14.7 points and 8 rebounds per game and is a contender to win the Rookie of the Year Award.

One of Cleveland’s best moves was the trade for Jarrett Allen last season, part of a four-team deal that landed James Harden with Allen’s former team, the Nets. The 23-year-old Allen — a strong rebounder and finisher around the rim — is now one of the best centers in the N.B.A. and was selected as an injury replacement for Harden in this year’s All-Star Game. The Nets have a worse record than the Cavaliers and traded Harden to the Philadelphia 76ers last week. They’ve looked very much like a team that could use Allen.

But this year’s success for Cleveland is not just because of the young players. Kevin Love, a five-time All-Star and the only James-era holdover besides Osman, has battled injuries for most of Cleveland’s rebuilding process. Love, a power forward, signed a four-year $120 million extension to remain in Cleveland entering the 2018-19 season, after James left the second time. Before this season, it looked like a mistake for Altman. When Love did play, his body language was sour. On multiple occasions, he openly showed displeasure with teammates.

Deng Adel, who played 19 games for the Cavaliers in the year after James left for the Lakers, said the early stages of rebuilding were “kind of tough” for Love.

“For the most part, he was still definitely a good teammate,” said Adel, who now plays for the Boston Celtics’ G League affiliate. He added: “It kind of gets frustrating, especially for where he’s at in his career. You know, you could kind of tell he kind of wants to win.”

After the trade for Allen and the drafting of Mobley, it seemed that there wouldn’t be room for Love. But in the summer, his agent put a stop to chatter that Love would try to negotiate a buyout. Instead, Love came back to training and told reporters he would be a “positive force.” Now, this year is among the best in his eight seasons in Cleveland. He’s averaging 14.2 points and 7.3 rebounds per game off the bench and shooting 39.2 percent from 3. Love is fitting in instead of fitting out, just as James once publicly preached for him to do.

“He’s a great mentor for us — for young players and especially the way he’s playing this year,” Osman said. “I mean, we’re really looking up to him. Offensively. Defensively. He’s crafty. He’s trying to help us. You know, everybody is doing something.”

Mentorship has also come from other sources. The veteran point guard Ricky Rubio came to Cleveland in a trade from Minnesota in the off-season and helped the team get off to a fast start with his steady hand in setting up the offense. But, in December, a knee injury ended his season, and he was traded in the deal for LeVert. Rondo has filled Rubio’s role.

If the Cavaliers make a deep run this postseason, perhaps it shouldn’t be a surprise. They have dynamic scorers (Garland, Allen), quality veterans with championship experience (Love, Rondo), and complementary shot-creators (Okoro, Osman). Especially this year, where there is no clear-cut favorite for the title, the Cavaliers have a real chance of making the N.B.A. finals. And they seem to enjoy playing with one another.

“A lot of times you can’t predict this type of stuff, man,” Knight said. “So the ingredients just work and there’s really not an answer for it.”

He added, “When you get a group of guys that are just unselfish and don’t care about which guy’s getting the points, all those type of things, I think it just works out.”

Of course, the Cavaliers still have a lot of work to do. The Eastern Conference is tightly packed and one losing streak could mean being exiled to the play-in tournament — and, perhaps, out of the playoffs. But this year has been an undeniable step forward. If nothing else, Cleveland is shooting for something bigger, to be defined by more than a past association with LeBron James.

“We’re trying to build something,” Osman said. “It’s all about these Cavs right now.”