Ritchie says he has simply not been good enough in recent weeks.
Ritchie cost the Magpies £12 million when they signed him from Bournemouth in the summer, and he initially starred on Tyneside.
However, though he has amassed four goals and five assists in 19 games for the club to date, he has been underwhelming in several of the club's most recent fixtures.
Though he has kept his place in Rafa Benitez's side, he has perhaps not been up to the standards that are expected of him in the past few weeks.
Ritchie himself certainly believes that. The Scotland international admitted that, although he was pleased with how he started life at St. James' Park, he has been disappointed with his own form of late.
He said, as quoted by Chronicle Live: "I am pleased with how I started, I felt fresh and sharp. The last few games I have not been at the races to be honest with you. I’d say that I have had a little bit of a dip in form and haven’t quite been at the levels I want to be at.
"In the last few games I have not been as good as I can be. Hopefully, I can up my form a little and help the team. There are not many players that perform at their top level throughout the whole season or their career. It’s how you deal with it when you do have a bad game or one or two bad games.
"You have to be mentally strong and that’s what I have been at the moment. I have had some good games but there is certainly more to come from me. I am certainly due a goal so that’s on my wish-list. I will be working hard to rectify the few quiet games I have had."
Newcastle fans will no doubt be pleased to hear that Ritchie is striving for better than he has been showing in recent weeks.
The team itself is in something of a mini slump this week. After winning nine games in a row, they suffered a shock defeat to Blackburn Rovers last weekend - only their fourth Championship loss of the season - and were knocked out of the EFL Cup on penalties by Hull City in midweek.