The 24-year-old found himself on the bench on Saturday as the Cherries lost 1-0 to Leicester after a run of seven starts since he last netted for Eddie Howe's men.
And Ritchie was honest in his assessment of his recent form.
He told the Daily Echo: "As an attacking player, people look at the goals you score and create and in my first six or seven games back, my form was very good.
"Over the past four or five games I have probably been a little bit off it and not quite my usual self. My legs have felt tired but I have started to gain that bit of fitness I missed out on at the start of the season.
"When I came back I felt fresh and while playing a lot of games over a short period at Christmas might have caught up with me a bit, that is no excuse. I wouldn't put my form down to that at all."