A four-match unbeaten run had lifted the Royals out of the relegation zone heading into the weekend.
They were, however, undone at Stoke City and saw fellow strugglers Aston Villa leapfrog them with victory over West Ham United on Sunday.
Reading were, however, unfortunate to come up short at the Britannia Stadium and Mariappa insists they remain optimistic regarding their chances of beating the drop.
"It was a tough game and they have some big boys - they used their attributes really well and in the first half I thought we stood up to that," he told the Reading Post.
"We're disappointed with the goals, but it's been a positive time for us and we will remain positive."
Reading are currently taking in some warm weather training in Dubai, with that trip seeing Mariappa and his Jamaica international colleagues Garath McCleary and Jobi McAnuff complete a gruelling period of travel which has taken them from Mexico to the Middle East.
He added: "We've done a lot of travelling and it does take its toll.
"You remain focused on the job in hand and when we flew out of Mexico we did all the right preparation and made sure we took care of the little things, like your hydration.
"But when the whistle goes all that stuff goes out of your head and you're fully focused. It's the same when I came back, but unfortunately we didn't get the result we wanted."
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