The former Real Madrid stopper was one of the most intriguing signings in a frenetic final few days of the Janaury tranfer window in which England's top-flight clubs spent record sums, with Chelsea alone splashing out almost 300 million pounds.
January signings can be hit and miss and it was a mixed weekend for new recruits.
Chelsea's British record signing Enzo Fernandez (22) enjoyed an encouraging debut in his side's 0-0 draw with Fulham while Leicester City's Australia centre back Harry Souttar (24) blotted his copybook with an own goal on his debut.
But Navas stole the show.
The three-times Champions League winner, loaned to Forest from Paris St Germain on deadline day, made a string of superb saves as his side sealed a crucial 1-0 win over Leeds United to push them further clear of the bottom three.
"Brilliant in the first half, outstanding and composed. The obvious talking points are the saves, and rightly so, he deserves all the credit for that," Forest manager Steve Cooper said of his new signing.
"But I loved his composure and game management and decision making, I really enjoyed that part of his performance. It was something that helped us win for sure.
"We've had a good few days with him where all he's shown is a real good work ethic, humility, desire to jump on board. We are really pleased he is here."
Argentina World Cup winner Fernandez, signed from Benfica for 107 million pounds, was on a hiding to nothing as he made his debut at home to local rivals Fulham, whose fans taunted him with chants of "what a waste of money".
OOZED QUALITY
But he looked the part in a deep-lying central midfield role, especially in the first half when he provided a platform for Chelsea's attacks and oozed quality.
He came close to a debut goal too, but ultimately it was a frustrating debut as Chelsea's attack misfired yet again.
Graham Potter also handed striker David Datro Fofana (20), signed from Molde, his Premier League debut as a late substitute and in 15 minutes he offered much more than Kai Havertz (23) and was denied a goal by a last-ditch clearance.
Leicester's Souttar, signed from Stoke City, enjoyed a winning debut as his side overcame Aston Villa 4-2, although scoring an own goal was hardly ideal.
But Souttar, along with fellow new signing Victor Kristiansen (20), impressed, although not as much as another new recruit Tete (22), who marked his debut with a goal.
"Tete is direct, can take people on and score," manager Brendan Rodgers said. "He's someone we've been looking for for a while. He was outstanding."
Experienced Craig Dawson (32) was signed by Wolverhampton Wanderers to bolster their defence but did even better than that, helping his side keep a clean sheet against Liverpool on his debut and scoring in a 3-0 victory on Saturday.
As for Tottenham Hotspur's new right back Pedro Porro (23), signed on loan from Sporting, he got no further than the bench in the 1-0 win over Manchester City but his presence seemed had a positive effcet on Emerson Royal, the man whose place he is supposed to take, with Royal having one of his best games.
"This is my team, this is Tottenham," the Brazilian defiantly posted on Instagram.
