McFarlane was put in temporary charge of the Blues for the FA Cup semifinal clash against Leeds following the sacking of Liam Rosenior and oversaw a 2-0 victory at Wembley on Sunday.
Enzo Fernandez scored the game's decisive goal with a header in the first half as Chelsea hit back following five straight defeats in the league without scoring a goal.
"It was important to break the momentum and the form that we were in," McFarlane told reporters after the victory.
"That completely changes the feel in the group and gives us confidence going into the next five games."
Chelsea now have an opportunity to win a first domestic trophy since 2018 when they take on Manchester City in the FA Cup final next month.
McFarlane also took charge of the Chelsea first team after the departure of Enzo Maresca in January, overseeing a 1-1 draw against Man City in the league.
"I knew what I was stepping into," he said. "It's easier this time because I have a relationship with the players and I've worked with them for three or four months now.
"I've been a part of the backroom staff, so I had a feel for what they needed psychologically. It's been intense."
Chelsea defender Trevoh Chalobah has insisted the players must accept their share of responsibility for the crisis that culminated in Liam Rosenior's dismissal, as the club attempt to steady themselves during a turbulent end to the season.
John Obi Mikel believes Cesc Fabregas needs more time before stepping into a Premier League head coach role, after the Spaniard was linked to the Chelsea job.
Matchweek 34 delivered drama across the Premier League, from individual brilliance at the top of the table to survival scraps, breakout performances and late twists shaping both ends of the standings.
Enzo Fernandez has again found himself at the centre of transfer speculation after being seen in Madrid less than a month after his controversial comments about Real Madrid.
