SANTA CRUZ — Seth Cooper was speeding down Interstate 205 when he asked his passenger, Warriors forward Alen Smailagic, to pull up the Dallas Mavericks’ roster on his iPhone.

For much of that 80-minute drive from Stockton to San Francisco last weekend, Cooper — a Golden State player-development coach — detailed the strengths and weaknesses of each Mavericks player. As he guided his 2016 Mazda 3 into Chase Center just an hour before tip-off, Cooper recited what he remembered from the Warriors’ game plan, which he hadn’t thought he’d need when it arrived in his email inbox.

But when forwards Omari Spellman (illness) and Eric Paschall (right hip bruise) were ruled out against Dallas, Golden State recalled Smailagic — a 19-year-old rookie — from the G League. Cooper, who navigates a split existence shepherding players between the NBA club and its minor-league affiliate, suddenly had to spend his Saturday night in San Francisco instead of in Stockton for the Santa Cruz Warriors’ game against the Stockton Kings.

To ensure he’s prepared for such schedule changes, he keeps workout clothes, a suit and a dress shirt at his Chase Center stall. Just like the players with whom he works, Cooper, 38, prides himself on his ability to adapt to any situation. It helps that his wife’s marketing job at Marriott allows her to work remotely. At a moment’s notice, she’ll pack an overnight bag at their Santa Cruz home and ride with Cooper to a team-provided hotel room near Chase Center.

“I’m lucky in the sense that I’m pretty flexible,” said Cooper, who left his job as an assistant coach at Illinois-Chicago last summer to replace Luke Loucks as the Warriors’ two-way coach. “I can be anywhere, and I’m good.”

Less than halfway through his first season with Golden State, Cooper has emerged as a driving force behind the team’s productive youth movement. When Smailagic, Jordan Poole or Ky Bowman is in the G League, Cooper serves as an extension of Golden State’s staff, working with Santa Cruz head coach Kris Weems to carry out each player’s development plan.

Cooper’s individual skill workouts are designed to fit the player’s needs, offer a go-to routine and fuel good habits. With Cooper’s help, Bowman — a score-first point guard at Boston College — has learned how to read defenses and run an NBA offense. When Cooper saw Poole’s confidence lag as he struggled to capitalize on big minutes early in the season, Cooper peppered Poole with encouraging words, reminding him that he was drafted in the first round for a reason.

When Cooper noticed that Smailagic slightly bent his elbow on his jump shot, he mapped out drills to help Smailagic keep his arm at a 90-degree angle. Now equipped with a quicker, more efficient release, he is shooting 51% from the field in the G League and 58.3% in limited NBA minutes.

“Having someone watching us as closely as he does, it definitely helps a lot,” Poole said of Cooper.

The Warriors were one of the first NBA teams to employ a two-way coach when the league introduced two-way contracts at the start of the 2017-18 season. Allotted up to only 45 days with the big club, two-way-contract players live a strange existence — they’re on two teams, but sometimes they feel as though they don’t have one. The two-way coach provides a consistent link to Golden State.

Though this is his first season in this specific role, Cooper has spent more than a decade in player development. Stops with the Clippers, G League’s Maine Red Claws and multiple college programs helped him iron out his simple, hands-on approach.

When his former teammate at Division III Edgewood College, Warriors assistant Chris DeMarco, told him last summer that Golden State might have a player-development opening, Cooper immediately was interested. The Warriors have served as a blueprint to him of what can happen when talent and quality coaching intersect.

“He’s been very helpful for me, understanding the message that Steve (Kerr) and the Golden State staff is trying to impart on the guys,” Weems said. “The main thing is that we just stay consistent with that. Seth’s active on the court. He jumps into our practices.

“He really helps us out all around in terms of helping us develop the guys. At the same time, he’s that bridge between Santa Cruz and Golden State.”

Game on Thursday Who: Warriors (9-26) at Minnesota (12-20) When: 5 p.m. TV: NBCSBA Radio: 95.7

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Cooper works with DeMarco, who oversees the player-development department, to map out his week-to-week schedule. But as Cooper’s last-minute trip to San Francisco with Smailagic illustrated, that inevitably is subject to change.

After Smailagic posted five points and five rebounds in 20 minutes of Saturday’s 141-121 loss to Dallas, Cooper drove to Santa Cruz for the Santa Cruz Warriors’ game the next night against the Texas Legends. Workout clothes, a suit and a dress shirt were awaiting him at Chase Center should he need to head back north for whatever reason.

“You have to be ready,” Cooper said. “Who knows what’s going to happen?”

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com Twitter: @Con_Chron