The Scot, 28, ended an eight-match losing run against the world number one to prevail 6-4 4-6 6-3 in Montreal.
"For Andy, it's all about adding to the two Grand Slams he already has," said Baker, a former Davis Cup player.
"Everyone involved in the game assumes that to win more he's going to have to get past Novak Djokovic."
Murray beat Djokovic to win the US Open in 2012 and did so again to triumph at Wimbledon in 2013.
However, Sunday's success in Canada was his first against the Serb since he ended Britain's 77-year wait for men's singles glory at SW19.
"It's a huge win for Andy," added Baker, who is now a BBC pundit.
"Although Andy's consistency in the Grand Slams has been unbelievable throughout his career, he is in such a tough era.
"A top athlete would never admit it, but you definitely get these psychological barriers.
