The West Brom midfielder gave his side the lead in Wales on Friday night, only for Gareth Bale to score twice and claim all three points for the hosts.
The result means the Scots remain winless in Group A, and are five points adrift of a play-off place after just three games.
"There is probably a little bit of hope if we win in Belgium,” Morrison told reporters after the match.
“We get that belief again and that's all we can do.
"We've got to regroup quickly or else the group is going to pass us by.
"Basically, we've got to win in Belgium. We've just got to remain positive, that's all we can do.”
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Scotland travel to Brussels in search of an unlikely victory against Belgium, who are unbeaten at the top of the table and beat Serbia 3-0 away on Friday.
"They are probably the favourites for the group and they've got some great players but we can't think too much about it,” Morrison continued.
"We just need to get on with it and look forward to the game. They are a good team but football is a funny game.
"We will go there and try to regroup and get a game plan and take it into the Belgium game."