Brian McDermott's side visit Swansea on Saturday with only two points to their name, and they currently sit 19th in the table. Despite struggling in the early weeks of their first top-flight season since 2008, Mariappa reckons the Reading squad are still full of confidence.
"The mood in the dressing room has always been the same," he said. "We know what we are capable of and what we can do, obviously people write us off early doors being the team that is newly-promoted."
Jamaica international Mariappa joined Reading in the summer from Watford but the 25-year-old had to be patient in waiting for his first-team opportunity. That came with a start in the Capital One Cup success against QPR and he retained his place in the starting XI for the draw against Newcastle last weekend.
Mariappa believes the squad assembled at Reading is a strong one and he will have to work hard to hold down his starting berth.
"We have got a good squad here and all the lads are getting fit and raring to go," he said. "I think all over the pitch you have seen numerous people playing this season so the competition is very high for places and it keeps everyone on their toes and when you get that opportunity you just want to take it."
The 2-2 draw at home to Newcastle on Saturday saw Reading throw away the lead twice, although Magpies striker Demba Ba clearly diverted the second equaliser into the net using his arm.
The decision to award the goal was berated by McDermott and Mariappa agreed that the players were also upset with the referee's call and hopes Reading benefit from some good fortune before too long.
He said: "It is disappointing to lose a goal at any time but especially a dubious goal. That is just the way things are and we will just get on with it and move on. The performance was good and that is the main thing, it will stand us in good stead this weekend.
"It is the old cliche - you hope it evens itself out over the season, as long as we don't get too many of those decisions I'm sure we won't be complaining."