Prior to becoming the head coach for the national team, he was the water polo coach at UCLA and California State University, Long Beach, beginning in 1985. At Cal-State Long Beach, Baker was a star player.
Baker coached both the men's and women's water polo teams to national championships. The men's team won the NCAA championship in 1995, 1996, 1999 and 2000, while the women's team won the national collegiate championship in 1996, 1997 and 1998. Both of his teams won a national title in the same school year twice (1995–96 and 1996–97), a first for a coach. In his first year at UCLA, he was named American Water Polo Coaches Association Coach of the Year for leading the men's water polo team to a second-place finish in the NCAA tournament.
At the 2008 China Summer Olympic games, his American team lost 8–9 in the championship game to the Netherlands, and the team took home the silver medal. "Head Coach Guy Baker has presided over one of the most dominating runs for women’s water polo the last eight years plus and with 10 first time Olympians on the roster the future looks very bright for this group," according to USA Water Polo.
