The Houston Rockets' #2 pick faced off against Cade Cunningham and the Detroit Pistons for the first time in their careers at Summer League in Vegas on Tuesday ... and it didn't disappoint.

Green outdueled the top pick with 25 points, 5 rebounds, 3 assists and 1 steal in the 111-91 win ... with Cunningham earning 20 points, 4 rebounds, 2 assists, 3 steals and 1 block.

Look, we get it -- it's Summer League, not the real thing, but it's exciting to see these guys go at it for the first of, hopefully, many times.

19-year-old Green was asked about his motivation to ball out ... admitting he really does have a grudge for not having his name called first at the draft last month.

"My chip's been super big," the Cali native said. "It started at draft night when I got drafted #2, I felt like I was #1."

"It's just the work I gotta put in. I keep a chip on my shoulder from where I'm from, my family installed it into me. So, Imma just keep getting better every day."