They won that match against Brighton 1-0 on Easter Monday, and Rawson played the full ninety minutes for Steve Evans' side. The problem was that his 28-day youth loan had expired the day before, so he was ineligible to play in the match. Evans said after the game that his loan had been extended until the end of the season, but instead he returned to Derby County before he could play another match.
Rotherham have also been fined £30,000 for the incident, which isn't the first such example of a club fielding an ineligible player this season. Blackpool were fined the same amount for playing Donervan Daniels against Millwall back in August when his loan had already expired, but they escaped a points hit - presumably because they lost the game anyway, whereas Rawson helped Rotherham to three points, which have effectively been chalked off.
So how does this affect Reading? Well, we head to New York (...Stadium) next Tuesday night to face the Millers, a game which suddenly has far more importance for the home side. They were four points ahead of Millwall and five ahead of Wigan Athletic heading into this weekend's matches, but that gap has now been reduced to one and two respectively. With a sense of injustice likely to be in the air on Tuesday night, you can expect Rotherham to come out fighting.
In another sense it may change the team Reading put out. We saw on Wednesday night that Steve Clarke experimented in effectively a dead rubber against Birmingham City, putting the likes of Andrija Novakovich and Jack Stacey on the bench. He's also said that Reading have a responsibility to the League to respect those teams with promotion and relegation on the line. Rotherham could still be safe by next Tuesday night if they win this weekend and both Wigan and Millwall lose, but that's far less likely now with the reduced gap. Had the game been "meaningless", we probably would have seen similar rotation to that of Wednesday night.
Rotherham can appeal the decision and have until Friday 1st May to respond. It could mean that the relegation battle is decided in the courtroom, long after the season ends.