With Fernando Perez' unfortunate injury, we're looking at having an opening day centerfielder who doesn't actually play center. That means Gabe Kapler, Ben Zobrist, and Justin Ruggiano are going to juggle the position until B.J. Upton returns - assuming the Rays don't try something like Akinori Iwamura in center with Adam Kennedy playing second. Thankfully, there's not much of a difference between the trio over a handful of games span.
Kapler has played center sparingly over his last three seasons. Spending 251 innings in center for the Brewers is the most since 2001 as the everyday centerfielder for the Texas Rangers. Even with that limited exposure, Kapler's last three years of UZR are -0.9, -4.6, and 4.8. Essentially average, even when you account for an extra year of age. Say -5 < x < 5 runs.
Zobrist is a below average defensive shortstop and lacks a sample size in the outfield large enough to make any true assumptions about. I'm willing to call him a 0 < x < 5 runs defensive outfielder until proven otherwise. That makes him a -10 < x < -5 centerfielder.
Ruggiano also features a small offering in the outfield, albeit larger than Zobrist. We're talking 226 total innings with only 37 of those coming in the centerfield. Like Zobrist, I think he's a 0 < x < 5 outfield defender, and a -10 < x < -5 defensive centerfielder. Ruggiano also seemingly figures to be the least likely to secure a roster spot following the centerfield triangle to open the year.
If those projections are accurate, we're not talking much of a difference over 150 games, not along 10-15 games. Kapler's best case defensive scenario is about 15 runs better than what we would expect from Ruggiano and Zobrist, but there's always a chance they can fake a better defensive turnout or are simply better than we'd expect. Either way, 15 runs over 150 games is a run every 10 games.
That means, if the Rays have the worst possible scenarios occur in center over the first 15 games, we're still only looking at about a run defensively.
And don't count on the worst possible scenarios occurring, Zobrist has connections: