Just stay on the A52 until after it merges with the A453. You should then get in the left hand lane marked industrial estate, go down to the roundabout and turn left onto Thane Road and the immediately left again onto Lenton lane. Follow the road all the way to the end, and you should find the university sports fields (the car park looks vaguely like a farm). The baseball pitches are about 300 metres across the fields in the far corner.