Complex sentence: An attempt to retain his Commonwealth title also ended in the semi-finals, while running nearly two seconds outside his personal best, whereupon Greene withdrew himself from consideration for the 2014 European Athletics Championships because of lack of form and a failure to make the agreed qualification time.
Split into simpler sentences: An attempt to retain his Commonwealth title also ended in the semi-finals, while running nearly two seconds outside his personal best. Greene resultantly withdrew himself from consideration for the 2014 European Athletics Championships, because of lack of form and a failure to make the agreed qualification time.