Wales, who are in third place in Group D with 11 points from seven games, drew 1-1 with Armenia on Saturday. Page's side are five behind group leaders Turkey, while second-placed Croatia have 13 points.
Wales next face Turkey in Cardiff on Tuesday and will need to win the match, while hoping Croatia do not beat Armenia at home. If they fail to qualify automatically, Wales will likely enter the play-offs.
"Unfortunately it's now out of our control," Page told reporters after the draw on Saturday.
"It's not materialised as we'd like but that's life and we have to get on with it. It's about building momentum and, if it's a play-off in March, it's a play-off in March. If results go for us, we've still got an opportunity to qualify (automatically).
"We can only control what we can do, get the players in the right frame of mind, mentally and physically ready for Tuesday... We need to finish the campaign on a high. It's important to have some momentum if there is a play-off in March."
