The main difference is the INTENT behind each and every single shot in a rally.
I was watching the 03 oz final and clips from the 03 Wimbledon today and that is the main difference i think.
-used to be alot more calm and focused on the court. Would move on easy after mistakes or blown opportunities.
-MUCH better footwork than now. She used to be really on balance and position which enabled her to go for her shots and make them. Now she looks really awckward and out of balance at times, which makes her spray alot more balls and results in errors.
-Decisivness. Rena used to be really sure what she wanted to do with each and every shot, specially her serve, she knew exactly which type of serve she wanted and where she wanted it to be placed. This was even more prominent on the 2nd serve.
-more mental than anything.
-she used to play the big points alot better, now she often squanders break points or leads, before she used to convert her opportunities.
-technically, her forehand is still a bit jerky, we know she works on it, and at times its brilliant in matches, but i think her problem is her racquet face is too open when she takes it back, which makes it harder to generate topspin on her shots, and results in tons of balls flying out....by alot.