PG: Washington has John Wall, Jordan Crawford (who averaged 20ppg at Xavier), and Shelvin Mack (whom we all know for his Final Four runs at Butler). Kentucky has Marcus Teague and Doron Lamb. Huge edge to Washington.
SG: Washington has Crawford. Guys like Roger Mason and Maurice Evans (who were very solid college players) barely crack the rotation. Kentucky has Lamb and Miller. Again, edge to Washington, though not by as much as at PG.
SF: Washington has Rashard Lewis (a 6'10" former NBA star who is still pretty good) and Chris Singleton (6'10" All-ACC defensive stopper). Kentucky has MKG and Miller. I'll give this one a push or possible edge to Kentucky, but Lewis and Singleton would make life VERY difficult for MKG and are far better than Miller.
PF: Washington has Trevor Booker (former star at Clemson), Andray Blatche (6'11" guy who averaged 17 and 8 last year in the NBA), and Kevin Seraphin (a 6'9", 265lb widebody who shows promise). Kentucky has Jones (undersized) and Wiltjer (skinny). Huge edge to Washington.
C: Washington has Nene (a 6'11", 260lb load inside that dwarfs Davis) and Blatche. Kentucky has Davis and Vargas. Big edge to Washington here.
Kentucky has a fantastic college team with four guys who will certainly play at the next level (2-3 of them may be impact players). But Washington has a full team of NBA players. They have former college stars playing role player minutes. It's just a different level. Even the very best of college teams would likely get beat by the typical bottom feeder NBA teams. It's just the nature of filtering talent from one level to the next.