The 22-year-old Brazilian joined Manchester United this summer in a deal worth around £48m plus a further £2m in add-ons, having struggled to force his way past Moisés Caicedo and Enzo Fernández at Stamford Bridge despite loan spells at Strasbourg and Nottingham Forest along the way.
Since arriving at Old Trafford, Santos has featured in all four of United's pre-season fixtures and has swiftly won over supporters, including with a crucial defensive intervention early in Saturday's 1-1 draw against Paris Saint-Germain in Gothenburg.
Speaking exclusively to MUTV afterwards, he made clear how quickly he has settled.
"I feel so comfortable," he said. "Here now, it's my home. Since my first day, I felt at home and I'm so happy to be here and to play very well."
Santos has stepped into the void left by Casemiro's departure and produced a string of composed performances in the engine room, maintaining a high pass accuracy throughout the game against the Champions League holders.
He almost opened his account for the club a few minutes before half-time, rising to meet Harry Maguire's header only to see his effort sail over Matvey Safonov's goal, though the goal may well have been disallowed regardless. Reflecting on the contest, Santos struck a balanced tone.
"This match was a little bit hard you know, it's pre-season," he said. "For sure we are improving more and more and more."
United finished the game on top, registering seven shots on target compared to PSG's three, and Santos believes that dominance is something the squad can carry into the new season.
"You know, it's football, I think we played better in the first half and controlled more of the game, created a lot of chances, but you know, it's football, you have to train hard for the next game."
Emphasising his focus on winning every fixture, he added that the team's attention now turns to the Republic of Ireland, where United continue their preparations for the 2026/27 campaign, with matches against Leeds United on Wednesday and AC Milan on Saturday still to come.
"The focus is always on the next game, but now we have to train and recover well first. Then train hard to be ready against Leeds," Santos said.