When a club trades five prospects (including their minor league pitcher of the year) in exchange for a starter, they usually get an ace in return. But not the Cubs.

On Friday, the Cubs traded top pitching prospect Chris Archer, outfielder Brandon Guyer, catcher Robinson Chirinos, shortstop Hak-Ju Lee and outfielder Sam Fuld to the Rays in exchange for Matt Garza and two minor league prospects. Garza, who is coming off a career year, immediately fills the No. 2 void in Chicago’s rotation.

The key players for Tampa Bay were Archer and Lee. Archer went 15-3 during two different minor-league stints last season and won the Cubs’ 2010 minor league pitcher of the year award. Lee needs a couple of years in the minors to develop, but he’s regarded as a skilled defender with excellent speed and good range at shortstop.

Considering Garza won’t be viewed as an ace in Chicago, it stands to reason that the Cubs overpaid. But GM Jim Hendry had to do something to improve his rotation and at 27, Garza is already in the prime of his career. He’s also coming off a season in which he compiled a 15-10 record with a solid 3.91 ERA and 1.25 WHIP. He averaged 6.6 strikeouts and 2.77 walks per nine innings and hitters batted just .248 against him last season.

He’s switching from the AL to the NL, so one would think that his numbers will only improve (or at the very least, stay the same). That’s huge for the Cubs, who desperately needed a top-of-the-rotation arm to go along with Carlos Zambrano and Ryan Dempster. The NL Central isn’t considered a powerhouse division but the Cubs will face Albert Pujols, Matt Holliday, Prince Fielder, Ryan Braun, Joey Votto and newcomer Jayson Werth on a consistent basis so they needed to beef up their starting five.

Besides, what constitutes being an “ace” anyway? Cliff Lee wasn’t very ace-like in the World Series and Tim Lincecum had an atrocious August before rebounding to help the Giants win a championship Usually when you think of aces, they have overpowering stuff. Well consider that Rays’ pitching coach Jim Hickey once referred to Garza as having “the best stuff on the staff” and the fact that he can throw his curve, slider and change for strikes will only help the 27-year-old at the smallish Wrigley Field. He also no-hit the Tigers last year, so clearly Garza has what it takes to be the “ace” of the Cubs staff, even if he doesn’t take the mound on Opening Day.

The bottom line, perhaps, is that the Cubs acquired a proven player for several unproven commodities. There’s always a risk in a deal like this that a club will get burned when a prospect they traded away turns into a star. But as of January 7, 2011, this looks like a deal that works for both sides.