Let's set aside Lewis and Smyth for a second; Lewis is basically flotsam and Smyth is a random left-hander who can provide Guy Hansen with a nice challenge next year.
No, the important players in this deal are obviously Cruz and Pratt. Cruz is thinner than "The Punisher"'s Oscar hopes, but that slender frame might well have to shoulder a substantial burden in the Braves' bullpen considering some of the options Bobby Cox has out there. (Antonio Alfonseca? Armando Almanza? Don Wengert? Jeff Reardon?)
There's certainly some doubt that Cruz can take up that load, and not just because Calista Flockhart took part in an intervention to get Juan to deal with his eating disorder. His stuff is electric, for sure. High 90s heat to go along with legitimately good breaking stuff make for an excellent K rate. Unfortunately those things tend to also make for command issues; ask Mike Macdougal how his arsenal effects his control. But the upside on Cruz is nearly limitless. If he can belie his body type and add some endurance than there's little doubt that he can be a top of the rotation starter. If his control improves, Cruz can be a dominating reliever. The former is certainly more valuable than the latter, but Bobby Cox has anointed Jaret Wright the team's 5th starter until Paul Byrd completes his quasi-annual rehab-setback-rehab-shutdown play, starring Mark Lester as the lovable scamp who just won't quit.
Pratt is somewhat intriguing, in that he's left-handed and he struck out more than a batter an inning last year, two things which will undoubtedly make him perpetually intriguing to various GMs and pitching coaches, no matter what road Pratt's career takes.
But he does all that without Cruz's easily tangible upside or electric stuff, and that certainly matters. Damian Moss with a strikeout pitch can be useful, but Cruz can be so much more than that, and he can be so much more than that this year.
No one likes to see his team acquire a pitcher with a 2003 ERA of over 6, but DIPS indicates that he was really unlucky with the Cubs, saying that his ERA should have been in the 4.15 range. His K/BB ratio in the big leagues was better than the 2/1 cutoff point, and between AAA and the majors he allowed only 8 homers in 111 innings. During that same span he walked 3.1 batters per nine, which isn't ideal, but doesn't indicate somebody with hopeless control issues. Cutting the trade down to its bare-bones, the Braves got the best player in the deal, and that's vital. It's a high-reward trade with little in the way of risk; it's sort of greedy to ask for more than that. The off-season hasn't been an easy one for Braves' fans, and Spring Training hasn't done much to inspire confidence. But this move helps.