The 22-year-old scored late in the first half as he cut in from the right to fire a deflected shot past Nikolay Mihaylov and end their Euro 2012 qualifying campaign on a high.
The recently-crowned Wales Footballer of the Year also it the bar with a fierce volley as he produced the latest in a string of superb performances for his country where his trademark pace and trickery have scared full-backs witless.
Wales finished third in their group behind England and Montenegro and Speed said: “Gareth was phenomenal again. He is a match winner. He works harder than anyone and that’s the situation we need if we are to keep improving.”