The 19-year-old Belgian forward became Newcastle's eighth signing of the European summer and could make his debut when the Magpies host Bournemouth at St James' Park on Saturday.
Newcastle head into the game looking for consecutive Premier League victories after Anthony Elanga and Yoane Wissa scored in the second half to secure a 2-0 win at Tottenham last weekend.
Jaissle said Fernandez-Pardo has already impressed in training and highlighted his pace and physical strength.
"For a young age, he is already showing a lot of strength on the pitch," Jaissle said. "His physical levels are really strong for our idea of how we want to play football.
"That speed up front can cause many problems. He is versatile, which gives us the freedom to adjust from match to match."
Fernandez-Pardo is fit and has trained with his new teammates, although Jaissle admitted the club will be careful with his workload after the youngster went some time without completing a full 90 minutes.
"He is fit and training with us," the Newcastle boss said. "It has been a while since he played a full 90 minutes, so it is important for a young lad to adapt towards our intensity in training but also in the Premier League.
"We will have a close eye on him and be smart with the load management."
Jaissle was also pleased with Newcastle's work in the transfer market, with the club focusing on building a young squad with significant potential.
"I am happy. A great job from Ross (Wilson) and his team," he said. "A clear idea with all of the signings, a young squad and signings with huge potential.
"That's a brave way because it's the way we want to go. We are aligned on everything. I am excited to work with the players."
The manager also wished Nick Woltemade well after the forward joined Juventus on loan for the 2026/27 season.
"I really appreciate Nick as a player, for his quality on the pitch, but I also appreciate him as a human being," Jaissle said.
"He has decided now to take another challenge. Hopefully, it goes well. I'm really optimistic that he will shine there and score a lot of goals."
Meanwhile, Amar Dedic has made an impressive start to life at Newcastle, registering three assists in his first three games.
"Amar has been exceptional so far," Jaissle said. "I'm really pleased with how fast he has adapted to the league, team and the playing style.
"He knows how I want to play football from our time in Salzburg. Amazing start, hopefully he can continue in the same way."
Jaissle also praised Elanga and Wissa after their goals at Tottenham, saying both forwards are benefiting from their hard work.
"We are really pleased that they have shined in the beginning of the season already," he said. "They are working hard to get these rewards and we support them."
Manchester United surrendered their advantage to draw 1-1 with Tottenham Hotspur at Old Trafford on Saturday evening, missing the opportunity to claim their second Premier League win of the campaign.
Chelsea bounced back from their defeat before the international break with a convincing 5-1 Premier League victory over Bournemouth at Stamford Bridge, as Jordan Henderson scored his first goals for the club.
Arsenal came from behind to secure a hard-fought 2-1 victory over Leeds United at the Emirates Stadium on Saturday, showing resilience to claim maximum points after falling behind in the second half.
Cole Palmer has signed a one-year contract extension with Chelsea, keeping the England international at Stamford Bridge until 2034.
