You say short corners didnt work at least 3 occasions, but how many times does lumping it in the box not work, and a centre half just clears it, and launches a counter attack? Yes it worked twice, but at a higher level that wont happen all the time. Short corners are needed, they can exploit lack of organisation (if the attacking teams sharp) and pre season offers the chance to work on these. Obviously not every short corner will work in the same way as you dont score from every corner which is crossed in the box. From what i can see (from the highlights) one very nearly came off. If you just lump the ball into the box at every attempt, better teams will become accustomed to defending against you and will pick you off. Variety is important imo.