A closer look at Guptill's innings vs Sri Lanka

Yesterday, I witnessed one of the most unusual innings I've seen. Martin Guptill hit 58 off 34 balls opening the batting against Sri Lanka at the Bay Oval in Mt Maunganui.

It wasn't a particularly fast innings, nor a particularly slow one. It was a little faster than the average 50 in T20 internationals. (The median strike rate for 50's by openers in T20 internationals is 151.3, Guptill scored at 170.6. The upper quartile is 171.4, so Guptill's innings is in the second quartile). Here's a graph showing his innings compared to all fifties in T20I's scored by openers.

We can see that Guptill's innings doesn't really stand out from the pack. So why was it so interesting?