The 34-year-old, formerly of Newcastle, West Ham and Liverpool, gave the Championship strugglers a crucial lead against Luton Town at the Madejski Stadium.
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Early in the second half, Carroll opened the scoring for the Royals with a header from a corner.
However, he went from hero to zero on 56 minutes as he was given his marching orders by referee Tim Robinson when it looked like he had got his and Reading's second with another header.
talkSPORT's Alex Crook recalled the incident: "He was claiming a second goal, cross from the right-hand side, it looked like he headed it into the net.
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"Actually, he did a Diego Maradona, he punched it into the net! A red card, and the goal disallowed."
Carroll, who initially signed a four-month deal at Reading last summer, has scored nine goals for the club this season.
However, he is now set to miss their upcoming match against play-off hopefuls Coventry this weekend.
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Matters were made worse for Reading as Carlton Morris scored in the 81st minute for Luton to seal a 1-1 draw.
The result for Reading sees them sit in the relegation zone and one point from safety with three games left to play.
Luton, on the other hand, remain third and are set to play in the play-offs in the coming weeks.