Hi Mate,
Number one thing to remember is the general rule of shutter speed = 1/focal length for a guideline of min shutter speed. This is of course assuming that you are hand holding (just an educated guess).
So with your 150mm lens, your min recommended shutter speed would be 1/150th of a second. You could have got this a few ways - bumped your ISO (400 or 800 is generally still quite acceptable), sacrificed that extra stop (the DOF is pretty good for f4, so you probably could have got away with f2.8), or as you said - use a flash.
With that said however, it doesn't seem to have much in the way of camera shake etc., but every bit of shutter speed helps. Shooting anything that is fast moving, i will ususally use up to ISO 800 even during the day to get as much shutter speed as i can - assuming i want it to be clear and frozen in action.
Rob