He's small @ 5'11"/6', but with some gained strength,heady play, and his leaping ability (had a vert well into the 40's) he should be able to hold his own.
I think he will be okay... better athlete that JJ, taller than Nate. (they're good players also, as you know and expressed)
I think the one thing good about the Mavs PG position (if they get mo) is all three has proven to get hot at times... so the Mavs can respect the hot hand on a nightly basis, they're all Vets, smart, and respect the process.... three headed monster might just be the ticket... we'll see.... not a Mavs fan, but I love Dirk, Monta & Rick..... wouldn't mind seeing them up end the "unstoppable" Spurs.....
PS.... you can kinda add Ricky Ledo into the mix.... although he's more of a two...