The all action midfielder, who got his first start for the club against Villa in the Premier League, is set to face the Birmingham-based club at Stamford Bridge again.
Niguez, who signed on deadline day in a loan move from Atlético Madrid, has not shown his best qualities for the Blues so far.
Asked about Saul, manager Tuchel told reporters: "Of course, we want to give Saul some minutes.
"First of all, the guys want to show and impress and keep on pushing. We need some players to have more competitive minutes and be a competitive team.
"We need them to have the opportunity to push some guys and to trust them also in a competitive cup match like tomorrow. Saul is one of them."
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