Last one of these.
5. Alex Gonzalez (0.9 WAR)
Sea Bass was a Red for 3 seasons. I know, how crazy is that? He had a great year in 2007, OPSing .793, but missed all of 2008 and came back and was awful in 2009. He spent most of spring this year with the Orioles, but was traded to the Tigers in the last week.
4. Felipe Lopez (4.2 WAR)
Lopez was a Red from 2003 to 2006, coming up in the Toronto system as a highly touted prospect and still was young during his Reds tenure too. 2005 was his breakout year, where he hit .291/.352/.486 as the Reds' starting shortstop. He was traded in The Trade, and went on to play for 7 other organizations.
3. Zack Cozart (4.8 WAR)
Most of this is defensive, but he's the incumbent #2, which means this number is only going up.
2. Gary Redus (5.1 WAR)
Redus came into the league in 1982 and was a Red until 1985. His rookie year was pretty eventful, as he finished 4th in the Rookie of the Year voting with a .247/.352/.444 line (and 39 stolen bases). He played all over the outfield, but spent most of his Reds tenure in LF.
Trivia: who finished above Redus in the 1983 Rookie of the Year race?
1. Ernie Lombardi (6.3 WAR)
Lombardi gets this honor because he deserves to be recognized and this is the best place to put him. As mentioned before, he wore 6 different numbers as a Red, with #2 coming in 1936 and 1937. Even then, that WAR number is good enough for him to top this list, but he had 31.3 total WAR as a Red.