The Royals defeated Wycombe Wanderers 1-0 on Tuesday night to overtake Bristol City, who were beaten by Middlesbrough.
Reading are now one of just two unbeaten sides left in the Championship, along with Bournemouth, and sit three points clear at the summit of the table.
However they put in arguably their worst performance of the season in the first half against Wycombe before Lucas Joao's sixth goal of the campaign in the 64th-minute gave them all three points.
It has been a remarkable start to life as Royals boss for Veljko Paunovic, with his team winning five out of six games so far and also recording five clean sheets.
Incredibly, they rank bottom of the division for average shots taken per game (7.3), but as Tuesday night proved, they only need one to win a game.
It is now just two wins in 51 Championship away games for the Millers, and their record on the road at Reading is not one to be admired either.
They have won only once in 24 trips to Berkshire – in May 1977 - and it means they have never won at the Madejski Stadium, which opened in 1998.
The good news for Rotherham is that Paul Warne will be back in the dugout on Saturday having completed a period of self-isolation after one of his family members tested positive for coronavirus.
Warne has admitted that he has "felt like a fan" watching the last two games from home, so will be pleased to be able to be barking orders on the touchline once again.
Reading Championship form: WWWWDW
Reading form (all competitions): LWWWDW
Rotherham United Championship form: WLDDLD
It was a poor night against the Chairboys for Yakou Meite, and Sone Aluko is waiting patiently to take his place on the right wing.
Veljko Paunovic confirmed on Tuesday that striker Sam Baldock would miss the next month with a calf injury.
Former Royals academy player Angus MacDonald remains suspended for Rotherham following his red card against Norwich City.
It has been confirmed that fellow defender Clark Robertson will be out until the new year after suffering a foot fracture.
Reading possible starting lineup:
Rafael; Esteves, Morrison, Moore, Richards; Laurent, Rinomhota; Meite, Olise, Ejaria; Joao
Rotherham United possible starting lineup:
Blackman; Harding, Ihiekwe, Wood, Mattock; Crooks, S. MacDonald, Barlaser; Wiles, Ladapo, Sadlier
We say: Reading 1-0 Rotherham United
Low-scoring wins could become a theme for Reading this season and all the signs point towards that happening on Saturday. Paunovic has made the Royals a clinical side, and that will be key against a resolute Rotherham team.