If you exclude the metatarsal fracture, he's spent more than twice as much time injured over the last three seasons as he did in the preceding six, 126 vs 60 days.
If you include the metatarsal fracture, it's 126 vs 165 days, though in both periods he missed 29 games through injury (for a total of 58 over 9 seasons.)
I guess my point is that Smalling was never injury prone. Wayne Rooney was never considered as such, and he spent about as much time as Smalling out injured. In the seven seasons they were both here, Rooney spent 258 days out injured, missing 57 games. Smalling spent 256 days out injured, missing 50 games. He was unlucky and had a couple of semi-serious injuries within months of each other a couple of years back, which cemented his status as 'injury prone', but he had that reputation before those injuries as well.