Ellison was a 22nd-round selection by the San Francisco Giants in the 2000 amateur draft out of Lewis-Clark State College, an institution that also counts former closer Keith Foulke among their alumni (as an aside, Jason Bay was also selected earlier in that round by the Montreal Expos--that's one heck of a steal!). Ellison was initially advanced at a slow and steady pace, and showed fair performance for a mid/late round pick in the low minors. Then, in 2002, he made the leap from A+ ball to AAA and held his own. He made his major league debut in 2003 at age 25, and got significant playing time for the 2005 Bondsless Giants.
Unfortunately, he did not perform well when given that opportunity, and in '06 was relegated to the role of Barry Bonds' designated late inning pinch runner. As a result, he had the very rare distinction of appearing in more games (85) than he had at-bats (81)! Acquired by the Mariners in return for a minor league pitcher near the start of this season, he has had little playing time in Seattle, who ultimately allowed him to depart via waivers to the Reds.
What those stats reveal is a guy who makes good contact, but but doesn't walk much either. While he flashed good doubles-power in AAA, his power has been virtually absent at the major league level in over 500 plate appearances. He's not a particularly good singles hitter either, with a MLB line drive rate around 17%. He has some speed, stealing 27 bases in '04 with Fresno and 14 bases with the Giants in '05. But as is so often the case, his success rate, while not horrible, has been bad enough that his base-stealing escapades have actually cost his teams more runs than they've produced.
One place we might hope to see exceptional performance from a player like Ellison is his defense. Here are his career major league defensive performances according to UZR, through May of this year:
Now, being an average center fielder certainly isn't a bad thing, especially for the defensively challenged Reds. But when combined with his performance at the plate (career VORP = -6 runs) you get a picture of someone who is essentially the definition of a replacement player. And at 29, he's unlikely to get a whole lot better.
That's ok, of course. He was, after all, acquired via the waiver wire, and probably is about on par with someone like DeWayne Wise to fill in the 5th outfielder spot on the club for the time being. Just don't expect a whole lot from him.