CREATE TABLE table_46166 ("Res." TEXT, "Record" TEXT, "Opponent" TEXT, "Method" TEXT, "Event" TEXT, "Round" FLOAT, "Time" TEXT, "Location" TEXT)

How many rounds did Brett go for the Strikeforce: Shamrock vs. Diaz match?
SELECT "Round" FROM table_46166 WHERE "Event" = 'strikeforce: shamrock vs. diaz'
SELECT "Round" FROM "table_46166" WHERE "Event" = 'strikeforce: shamrock vs. diaz'