That will almost certainly hurt your speed. Also, I think that the type of training you're doing probably isn't even the best for field hockey. As you know, field hockey is similar to soccer in that you have alternating bouts of sprinting, jogging, and rest. Going out for long slow distance runs (at least not 4 days a week) is not the best way to prepare for this type of a game. You should probably be including some fartlek running and also some short sprints. If specific endurance was what you were looking for, you could even do short sprints (30-40m) with minimal rest (30-45 sec). This would probably be a closer simulation to what you'd experience in a game than steady state slow running.