United expressed "disappointment" after Vale boss Michael Brown claimed Saiz spat in the face of one of his players early in the second half of the match.
Saiz, signed for a reported £3m from Spanish club Huesca in July, went on to mark his first appearance in England in style.
A Leeds spokesman said: "We are disappointed by the allegations made following our game against Port Vale last night. We are also disappointed by the treatment of our players throughout the match. Our player denies the allegation and we are confident that the referee's report will vindicate him."
Vale defender Gavin Gunning was sent off towards the end of a stormy encounter which saw frustrations also spill over into the tunnel area.
Brown, who spent three seasons at Elland Road before departing in 2014, made the spitting claim immediately after the match.
He said: 'The guy who scored three goals spits in Joe Davis' face in the 40th minute and it is very hard to take
''So that certainly knocked us off balance
We asked their staff to take him off, they ignored that and he scored three goals
''That is why it was getting a bit heated down in the technical area.''
Source : PA
Source: PA