Aitor Karanka's men were 1-0 winners over Wigan Athletic on Friday, as Patrick Bamford's first-half goal proved enough to seal the victory.
Watford then left it late to get a 2-2 draw at an out-of-form Derby side who, despite now being seven matches without a win, are still in the hunt themselves.
The visitors were down to 10 men and trailed 2-1, but Odion Ighalo's late goal secured what could prove to be a crucial point in the final reckoning.
With Bradley Johnson's strike earning Norwich City a 1-0 triumph at Brighton and Hove Albion, Ipswich Town and Bournemouth sharing the spoils in a 1-1 draw, and Brentford thrashing Fulham 4-1, the battle for a place in the Premier League is closer than ever.
Incredibly, two other sides - Ipswich and Wolves - will consider themselves as contenders, too, sitting level with Derby and just six points behind second-placed Bournemouth.
Wolves claimed maximum points in a 2-1 success at Nottingham Forest to keep alive their hopes of back-to-back promotions.
Even the fight to avoid relegation could go the distance, with Millwall's 2-1 win over Charlton Athletic ending a nine-match streak without a victory to move to within four points of safety.
It is Rotherham United who they are chasing and manager Steve Evans appears to be feeling the pressure after Birmingham City inflicted a 2-1 defeat on them.
Evans saw a penalty claim for his side waved away as they chased a leveller and later blasted referee Dean Whitestone, saying: "It was the worst refereeing decision I've ever seen.
"You might as well get a 12-year-old who has blue blood in his veins to come and referee."
