OAKLAND — As the Warriors moved upcourt on a random second quarter possession in Chicago last Thursday, the basketball gravitated where it so often does when reserves are on the floor: Into David West’s hands around the mid-post.

West snatched it with his vice-grip, rose it above his head and surveyed the floor with those savvy eyes. What he saw was a scrambling Bulls defense out of position, overloaded to his right and undermanned on his left. Bobby Portis was the lone defender between Matt Barnes, flanked on the left wing, and Patrick McCaw, who had a free lane to the hoop.

West noticed the breakdown immediately. But McCaw, a wide-eyed rookie, didn’t for a brief second, jogging next to Porter instead of zipping right by him.

“Pat!!!” West yelled, startling the rookie into a realization. McCaw turned and located. West fired a laser. The Warriors picked up two points. On the way back down the court, West took time to teach the rookie a lesson.

“There are just windows that are always open regardless of who you’re playing against,” West said. “It’s a matter of guys knowing where they are.”

(Here’s video of the play. Turn it up and listen closely to hear West yell “Pat!!”)

Because of the addition of Kevin Durant, the Warriors reshuffled the make-up of their bench this season. Now with the ability to stagger the minutes of three of the best offensive talents on the planet, they opted for West, a more defensively sound big man, rather than bringing back Mo Speights, a scoring big with defensive troubles.

At times, they’ve missed the streaky shooting of Speights, maybe no more so than right now. Durant is sidelined for at least a month, so some extra scoring punch off the bench would be welcomed. But even at 36 years old with a once reliable jumper that’s turned flat, West has been a surprisingly effective offensive player in a different way. He’s one of the league’s best passing big men.

This season, West is averaging 6.6 assists per 36 minutes, an incredible number for a center — the 34th highest mark in the entire NBA. Everyone above him is either LeBron James, Draymond Green or a guard. Al Horford, at 5.4 assists per 36 minutes, is the next closest center.

West has 105 assists in 574 minutes. Shaun Livingston, the Warriors backup point guard, has 98 assists in 1,007 minutes. Last season, Speights had 61 in 832 minutes. What West is doing is extremely rare for a backup big. But it’s by design. Steve Kerr has turned West into a hub of the offense when he’s on the floor.

“We run a lot of actions for him to make a pass,” Kerr said. “He’s a brilliant passer from both the high post and the low post. He’s been fantastic. I just love what he gives us on so many levels.”

While at Team USA this summer, Durant asked Paul George about playing with West when he was with the Pacers. He got rave reviews. West has a rock-solid reputation around the league, earned over 14 sturdy seasons, which includes two All-Star appearances.

But his passing is never mentioned first, or at all. People talk about West’s toughness, his rugged screening, his on-court enforcing, his locker room leadership, even his crafty low-post touch that once made him a 20-point per game scorer.

But after just a few days in training camp, Warrior coaches and players were startled by just how adept West was as a passer. Kerr knew it was a weapon he could better utilize.

“Early in the year, we had a couple plays where I could’ve run a couple tricks off him, maybe a backdoor or set somebody up for a back cut,” Durant said. “He’d bring me to the side and let me know, this is going to be open. I’m like: ‘Nah, it can’t be. They’re playing me for it.'”

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But then the games started and West would give one of those grizzly head nods for a cut. Durant would try it. Then West would drop it in perfectly and Durant would get an easy two points.

“When I just shut up and listened and did it, I was open,” Durant said. “There’s plenty of times where he says those small things. He doesn’t talk a lot, but when he does, it’s impactful.”

Here’s an example from early in the season. Out of the high post, West gets a feed from Durant and slowly lets the play formulate. Durant circles around him, getting Luol Deng, a solid NBA defender, caught up in traffic, as West pops in a perfect pass over the top.

And here’s another example, this time with Andre Iguodala, another intelligent player who knows to keep his head up when West is on the floor. With nine seconds left on the shot clock and nothing formulating, West gets the ball out on the right wing. No one seems to be open. But West isn’t just looking at his offensive players, he’s surveying the defenders. Will Barton isn’t paying attention. West notices. So he just whips a pass right over Barton’s shoulder to Iguodala for a layup.

“Sometimes he just throws the ball and throws us into a basket,” Durant said. “We’ll be standing there and he just kind of tosses it into an area and we go get it.”

West hasn’t always been a high-volume assist man. During his early years in New Orleans, he played the pick-and-pop game with Chris Paul, who controlled the entire offense. West was a scorer, not a facilitator. Despite averaging nearly 40 minutes a night, he never averaged more than three assists.

In Indianapolis, West ran some high-low post action with Roy Hibbert. His passing was useful. But that was a defense-first Pacers team with a lack of space and shooters. They relied more on isolation and mid-range jumpers. Same with the Spurs last season — West’s lone year in San Antonio — when Gregg Popovich turned the offense over to Kawhi Leonard and LaMarcus Aldridge.

So this season, with the Warriors, is really the first time in West’s 14 seasons he’s been in an offensive system that so brilliantly fits his passing skill set. West is not an off-the-dribble playmaker. He’s a breakdown identifier with great touch, who recognizes angles to find guys layups. No one leverages those angles and passing windows like the Warriors.

“What we do here is sort of my comfort level, systematically,” West said. “A large part of it is just cutting, screening, movement.”

Against opposing bench units, who are often filled with young, inexperienced and flawed defenders, the Warriors love to post West up on the right block. The focus of the defense shifts toward him. Then behind the action, the Warriors run a combination of back-screens and cuts.

Iguodala and Klay Thompson and Durant and Ian Clark and others scatter around until one springs open. Then West zips in an on-point quick-strike, often with his left hand.

“He’s a 36 year old,” Durant said. “A lot of 36 year olds aren’t getting calls anymore. But there’s a reason he’s around.”

West has assisted on 20 different Klay Thompson layups this season. Here is one.

In that same game, on the possession before, here he is out of the post finding Iguodala with that left-hand quick strike.

Another example: Take a look at this beautiful over the top lefty touch pass to Matt Barnes (in literally his first play as a Warrior), leading right into a layup.