[4] He went on to feature regularly in the Italian amateur leagues,[1][4] while taking up several side jobs, including as a marketing rep for a software company and as a courier, in order to support himself financially.

[2][3][6] On 1 January 2019, Sartini joined Major League Soccer side Vancouver Whitecaps FC, as an assistant coach to Marc Dos Santos.

[13][14] On 29 August, Sartini took charge for the first time as Whitecaps' head coach in their league match against Real Salt Lake, which ended in a 4–1 victory at BC Place.

[14] With the squad being at the bottom of the Western Conference's league table at the time of his appointment,[1][5] Sartini managed the side to seven wins, five draws and two losses until the end of the regular season, collecting a total of 26 points in 14 matches and helping the club qualify for the Playoffs,[2][5][15] although the team eventually lost to Sporting Kansas City in the first round.

[20][21] On 5 November, during an MLS Cup playoff game against Los Angeles FC, Sartini received his first red card in Major League Soccer for verbally abusing referee Tim Ford in the stoppage time of the second half; moments earlier, Ford had accidentally collided with a Whitecaps player, preventing them from defending a counter-attack from the opponents that ended up in a goal, which was later overturned due to a delayed offside decision.

During his coaching stint at Vancouver Whitecaps FC, Sartini mainly used a 3–4–1–2 formation,[1][5] with an organised system based on zonal marking, high pressing and a quick and direct style of play, which allowed his team to break through the middle of the field and create chances via counter-attacks.

[2][11] When asked to elaborate on Ulivieri's impact on him, Sartini stated that he taught him how to analyse the opponent's tactics meticulously, saying quote, "What I learned from him is the desire to go deep into detail, try to challenge yourself every time and to find the new ways, new ideas.

"[2] The Italian has also gained notoriety for his eccentric personality, his enthusiastic interactions with the fan-base and his man management skills, showing respect for the most experienced players in the locker room while often giving motivational speeches to encourage the whole team.