DEL MAR, Calif. – The day before Del Mar was to open, and only days before his two best horses were to run in significant stakes races, trainer Jim Cassidy said he was “relaxed.” Not so the day before, when he was “very stressed.” But after The Usual Q.T. and Evening Jewel put in flawless works on the turf here Monday and were fine the next morning, Cassidy allowed himself to look forward to what could be a lucrative weekend.