you know You mostly described a winger in your description of his game right
Ok, I guess I'll clarify my comments then.
Good skater: Warren is quick enough to get back and defend the rush if his team turns the puck over in the offense zone. He's also shown a good ability to carry the puck through the neutral zone.
Sharp passer: He's shown a good breakout pass and cycles the puck well in the offensive zone.
Good positioning. Warren's exhibited a good sense of when to pinch and keep play in the offensive zone and when to fall back and defend. When skating back he's usually well-positioned to keep the opposing winger out wide. He keeps an active stick and shows a nice ability to interrupt passing lanes.
Shot effectiveness: He's got a solid, accurate shot and he shows a good awareness of when to keep the cycle going and when he's able to get his shot through.
But yeah, there's certainly room for improvement in other aspects of his defensive game. He's not the strongest guy on the ice, he's not going to bully anyone in front of the net. At 5'11 he's got a decent frame to fill out over the next few years though, he's not exactly undersized. Sometimes his pairing gets pinned in the D-zone for longer shifts and he's got to keep his awareness up.
Warren's a smart, fairly well-rounded defenseman with a good offensive skill set. He'd be second only to York among USNTDP defensemen on my board.