Sony have just released a 400mm f2.8 lens to a lot of fanfare and good reviews. They speak to its low weight and balance and ease of use for long periods of time especially when compared to the Nikon and Canon alternatives.
The bodies used in one review were top pro and 20mp, so mp cannot be an issue to professional sports photographers.
I was wondering therefore, how the oly 300mm pro lens with the em1 mkII would stand up in this environment. It is smaller, lighter, maybe faster and a fraction of the cost. The only perceived negative could be the sensor size, but you get the same dpi prints and most images end up in newspapers or on line anyway.