Lewandowski has scored 33 goals in the Bundesliga this season, 12 more than nearest rival Patrick Schick, to fire Bayern to a record-setting 10th straight league title with three games to spare.
The Poland international has found the net once every 81 minutes in the top flight this campaign, while no player has managed more than his 48 goals across all competitions in Europe's top five leagues.
However, questions persist as to the future of Lewandowski, who is entering the final year of his contract at Bayern, with Barcelona reportedly preparing to swoop for the 33-year-old.
Bayern sporting director Hasan Salihamidzic insists the talisman will not be sold to avoid losing him on a free transfer, but Lewandowski suggested no new contract talks have been opened by the club.
Nagelsmann, speaking ahead of Sunday's (AEST) visit to Mainz, reaffirmed his stance on wanting to keep his star striker at Bayern for as long as possible.
"It's always good when you have planning security in all areas of life. I've said it at least 50 times that of course I wish he would stay, nothing has changed this week. That's my point of view," he said.
Salihamidzic has already rebuffed talk of signing Borussia Dortmund's Erling Haaland, who will reportedly be available for a €75 million ($112.1 million) release clause at the end of the season, as a replacement for Lewandowski.
Nagelsmann echoed Salihamidzic's sentiment as he ruled out moving for Haaland, who has scored 82 goals and supplied 19 assists in 86 appearances in all competitions since his Dortmund debut in January 2020.
Pressed on comparisons between the two strikers, the Bayern coach responded: "These are two different types of players that you can't compare. It's like apples and oranges."
Lewandowski is likely to feature at Mainz, fitness permitting, but Nagelsmann confirmed he will be without Thomas Muller, who has 17 top-flight assists this term, the most of any player in Europe's top five leagues.
"Muller is ill and will not travel this weekend. We will try to give some players the opportunity to start," he continued.
"[Eric Maxim] Choupo-Moting will definitely be in the starting line-up, that much I can say for sure.
"The virtue of a winning mentality is noticeable in the lads even after the championship in training. My everyday life is a little more relaxed than in the middle of the season."
Bayern would surpass the Bundesliga record for most away goals in a season (47, a record set by Bayern in the 2019-20 season) with two strikes at Mainz, but Nagelsmann appeared uninterested by that feat.
"You always have to be a bit careful when it comes to respect for the opponent," he added on the possible record.
"Of course we always want to score a lot of goals, that's what makes football so appealing. It won't be easy, but we're trying hard to find goals and play a good game offensively."