The world No 1 proved he has fully recovered from a hip problem which had previously kept him sidelined since January.
Nadal cruised through the tournament, not dropping a single set in clashes against Aljaz Bedene, Karen Khachanov, Dominic Thiem, Grigor Dimitrov and Kei Nishikori.
But despite his stunning performance in the run up to Sunday's clash, Moya admits Nadal still felt he needed more practice before the final round.
"He played very well, feels well, is healthy, for him this part of the year is really important," he told Canal Plus.
"Winning Monte Carlo is very important.
Related articles
Yesterday (Saturday) he felt that had to practice a little bit more
"He doesn't surprise me anymore, he works so hard to constantly improve all the time.
"Yesterday (Saturday) he felt that had to practice a little bit more."
Nadal is now preparing for the defence of his Barcelona Open title this week.
His first match will be against Roberto Carballes Baena on Wednesday.
The 31-year-old will then remain in his native Spain for the Madrid Open in May.
Nadal must win both tournaments to keep his place at the top of the world rankings.