Spanish Mission was the one and only ride Boss had been booked to ride on Saturday and it was expected to send his career out on a high. However the dream end to a 37 year career wasn't to be.
The race itself was slowly run with the short priced Moody runner battling to keep pace with the leaders in the home straight and found wanting for a turn of foot to compete with Sound.
Sound led the field over the line with fellow roughies Dr Drill and Wentwood completing the trifecta whilst Boss brought Spanish Mission home in fourth.
Boss, who had won 90 Group 1 races coming into the day admitted the timing was right to hang up the saddle.
"To compete at the level I want to and I’m used to, and what’s required to compete at that level, you got to be all chips in. You got to be more than 100 per cent.
"I found myself just recently not fully invested and that was (the moment)," Boss told News Corp on Thursday.
Boss now heads into retirement amongst ravings elite with only Damien Oliver (126), George Moore (119), Roy Higgins (108), Jim Cassidy (100) and Hugh Bowman (100) having won more Australian Group One races than Boss.