The West Yorkshire club’s first game with fans attending for more than 14 months was ruined when Jordan Abdull swatted off some soft defence in the 78th minute to put KR in front for the first time in the entire game.
Playing in front of 3,600 supporters at their home ground of Wheldon Road as restrictions were finally lifted, Castleford had led 14-0 at one point and were also 20-12 ahead at the interval.
However, they imploded with some poor decision-making, handling errors and ill-discipline to lose for only the second time this year.
“It’s probably been coming,” insisted Powell, whose side had won six of their seven games this term.
“I don’t think we’ve been really playing that well.
“I thought Hull KR were really good with the ball; they challenge you a little bit differently to some other teams, have some really powerful players on their edges and we didn’t quite match up to that.
“In particular, our right edge got put under a lot of pressure.
Their left edge is playing some great rugby league at the moment and we just didn’t handle it.
“I don’t know what we were thinking at times.”
Castleford were erratic in the second period and Powell continued: “I go back to last week and we were a little bit like that in the quarter-final that we just won (against Salford Red Devils).
“Some of the messages we’re giving I don’t think are being heeded.
“It was disappointing.
“Defensively and discipline-wise as well, there’s some things there that quite a lot of the players need to take a hard look at themselves.
“And we all do. And we have all got to review and analyze ourselves .
“But we’re not going to be successful playing like that so we need to step up.”
Castleford went 14-0 up with a Danny Richardson penalty but George Griffin fumbled playing the ball in the next set and Rovers, who move up to seventh with a third win, began their rally.
Asked if that lifted Rovers, who scored with the first of two tries for ex-Tigers winger Ben Crooks, Powell said: “It does when you drop the ball on the first tackle in the next set.
“We got two and gave four away. That’s just the basics of the game. “There were some errors there that were just fundamental.
“Even then, we know we’re in front at half-time. We were eight points in front and come out and play so far away from a team that has any control about it that it’s untrue.
“I thought we did some ridiculous things at times.
“Things players playing at this level really shouldn’t do. There needs to be an honest discussion when we’re in on Wednesday and then we move on.
“It’s a short turnaround to Warrington (Wolves away on Saturday) and we’re going to need to be a lot better than that.”
Having fans back in their home for the first time in so long was an obvious positive of last night’s game.
But Powell said: “It is weird. Really strange.
“It was strange for me because of the current situation.
“We haven’t seen it for a while and it was weird coming down Wheldon Road and seeing all the fans.
“Obviously, that’s fantastic and it was great to have an atmosphere in.
“But we just didn’t do the fans justice, which is what we really wanted to do tonight. We just weren’t good enough.
“They’ll have gone home disappointed. And that’s the last thing we’d have wanted to happen tonight.”