"Scalping is the act of cutting or tearing a part of the human scalp, with hair attached, from the head of an enemy as a trophy. Scalp-taking is considered part of the broader cultural practice of the taking and display of human body parts as trophies, and may have developed as an alternative to the taking of human heads, for scalps were easier to take, transport, and preserve for subsequent display. Scalping independently developed in various cultures in both the Old and New Worlds." ---
en.wikipedia.org/wiki/ScalpingHere, #1 does not mean it literally (at least I really hope not), but is referring to the won game against a very strong player as a metaphorical "scalp".