The 33-year-old has struggled to make an impact at Chelsea since arriving from Barcelona last summer.
Leeds scored early in either half, first through Wilfried Gnonto just 55 seconds in, then Raphael Varane's own goal three minutes into the second period of the Premier League clash. First Pellistri played his role in a move finished by Marcus Rashford - shifted to the centre in the reshuffle - before Sancho made it 2-2. It was Sancho's first goal since the Europa League win over Sheriff Tiraspol on September 15, but the 22-year-old has been out of the first-team picture since a drop in form cost him the opportunity of a World Cup place, and only returned last week for his first appearance since October.
Last season's Sky Bet Championship winners booked a home clash with Leeds after a 3-2 fourth-round replay victory at Sunderland on Wednesday evening after cementing eighth place in the top flight with Friday's 0-0 draw at Chelsea.