His contact rates are still quite elite. Z-contact in 2015 was only 2.5% lower than in 2013 when he had a .400 wOBA. O-contact in 2015 was only 3.7% lower than 2014 when he had a .444 wOBA. Pull percentage has actually gone up.
It should be mentioned that his Z-contact, O-contact and pull % are all higher than the reigning AL MVP. I believe steamer and zips are both producing down case scenarios.
Also, regarding ballpark dependency: Matt Hollidays final three years at Coors saw a difference in home/road slugging of 207, 237, and 98 basis points. Tulo's final three full years at Coors saw differences of -103, 84, and 301. Holliday has gone on to produce similar wOBA and wRC+ numbers despite playing his home games in much more pitcher friendly environments than Rogers Centre.
I believe a year and nine months removed from surgery, combined with the comfort of starting the full year with the franchise will allow him easily the steamer and zips projections.