To me this is actually the biggest concern with Bagley. He's my pick for #2 as it stands now but I'm definitely questioning his fit in the modern NBA. If you meant "ability to keep pace" as flexibility offensively, motor to run the floor, and the ability to guard smaller players on a switch then I would agree with you.
But in the macro sense, I am concerned that Bagley is an old school PF in a league that is increasingly going away from the traditional PF and C lineups in favor of a ballhandler, three wings, and a big. I don't see Bagley ever thriving as the lone big in that setup so the question I have is if he's skilled enough to play as a pseudo wing. As a stretch/playmaking 4 who adds tremendous rebounding ability. If so, then he could be a key piece. But unless Giles really pans out or WCS finally realizes that hitting the boards and defending every night is what will get him paid it still leaves the Kings without a center and without a small forward.
As you know Bagley is an explosive player. He's fast twitch with superior agility and balance. Off the top of my head I am trying to think of front line guys faster than him changing ends. AD comes to mind. Ginanis comes to mind. Thats about it. Capella is pretty fast too. Randle runs well but Bagley probably has better leg speed and burst. So in my mind the question becomes not how is this kid going to handle the "modern NBA" but how is the modern NBA going to handle him?!
I think Bagley is 1-2 strides faster than Willie or Skal changing ends. And he runs constantly. What will happen is he will rim run with Fox or even ahead of him. If he does not get the pass he will collapse the D into the paint and leave wings or trailer open for catch and shoot or drive to hole. We will get early offense going just off his transition speed. I like this aspect of his game to put constant pressure on the D and increase our league worst pace.
He's also a perfect running mate for De'Aaron. Just on this aspect alone, I think you have to be almost sold. De'Aaron needs guys who can play his pace, play smart and finish plays.
Now instead of thinking in terms of whether Bagley can anchor a group in the middle with three wings and a PG or if he needs another big out there, I like to think in terms of adding impact players and letting them sort it out, forcing the opponent to adjust to us. For example, even if we add Bagley, I would not be opposed to adding Randle who would provide the most impact as free agent signee, even though others may think their respective skills overlap. (Yes I would rather have Randle than Gordon simply because he's a more impactful player.)
I would also not discount the idea of Bagley spending time as three (with Giles at center and space creating 4). He would punish wing defenders in the post. I think he has the versatility and agility to defend the perimeter and play effective team defense. We could exploit his high activity level this way.
I would exclude Willie from any prospective lineups. The glorious thing about our lotto luck and overcoming 90% odds and with this draft being loaded with bigs is we can draft Willie's replacement, subsequently package him in a trade, thus clearing playing time for Skal, Giles, Bagley (Ayton) or other free agent or trade targets. It would be fair to worry a frontline of Willie and Bagley would NOT solve our defensive issues. But we don't need to worry. His potential effectiveness next to Bagley or whomever is not relevant when every effort is made to find Willie a new home.
Now maybe the trade market is lukewarm or nonexistent for Willie. So be it. But the idea of building around Willie is a flawed premise. We have a three player core (Buddy, Boggy, Fox) and a bunch of guys trying to figure it out. I wouldn't let the plusses and minuses of WCS game affect who I take on June 21.