The 21-year-old has been a substitute for 12 games in a row and would have been a certainty to replace injured Wayne Brown from the start against Brighton on Saturday, just as he did for 53 minutes against Leyton Orient, but due to the terms of his loan deal from the Seagulls he will not be eligible.
Speaking to This is Bristol, Tunnicliffe said: "It's been disappointing for me over the last few months.
"The only reason I came away from Brighton was to play football, and, unfortunately, that's not really happened for me lately, for whatever reason.
"I would probably have got a game this Saturday, but it's just my luck that I can't play.
"I know there's another big game coming up on Tuesday, so I'll just train as hard as I can this week and hopefully be involved in that."