Alexis Sanchez's frustration at Arsenal's failure to qualify for the Champions League last season was central to his decision to join Manchester United, says Jose Mourinho.
Chile forward Sanchez completed his move to Old Trafford last month in a swap deal that saw Henrikh Mkhitaryan join the Gunners.
Sanchez is set to make his European bow for the Red Devils when United tackle Sevilla in the first leg of their last-16 Champions League tie on Wednesday.
Mourinho described the former Barcelona star as a player United "needed" and believes the 29-year-old's desire to play in Europe's premier competition was the motivating fact for his move.
"It is true that we have a new player, Alexis Sanchez, and we could have waited for the transfer market in the summer but we decided to go now in the transfer market," Mourinho said.
"We felt we needed him. Manchester United in the Champions League is quite a big thing, Alexis came with all his efforts to play on the Champions League stage.
"We know it has been hard for me as a coach to motivate my players for a competition we didn't want to play [the Europa League]. But because we won it we got to qualify for the Champions League so motivation is always there - we always want to play against the best teams.
"So Alexis wanted to come to a team to play in the Champions League."
Mourinho has won the Champions League as a coach with Porto and Inter, and enjoyed European success with United in the Europa League last year.
And the Red Devils boss feels his current squad is somewhere in between the sides he coached to success on Europe's biggest stage in terms of experience, but suggested his side are not among the favourites for the tournament.
"I won with Porto, very young, inexperienced team at this level, so many playing the Champions League for the first time," he added.
"It was the opposite at Inter, lots of over 30s with lots of players with great experience at high level but not successful.
"This squad is more in the middle a bit. We have some players with experience and others without experience but I think in the end I normally say Champions League dreams they start around the quarter-finals and not in last 16, it still looks a long way to go.
"When a team reaches the quarter-final, this is the moment. Even when they are not favourites, like us, they start realising anything is possible."
|Pogba: Kante, Matuidi have 15 lungs|
|Julian Nagelsmann: the Bundesliga prodigy swapping Hoffenheim for RB Leipzig|
|England dominate in Durham to close in on series whitewash|
|´Fortunate´ Federer closes in on Halle title|
|Calamity Caballero and Sampaoli tinkerings leave Argentina a broken mess|
|Wimbledon champion Muguruza confident despite Birmingham defeat|
|Argentina 0 Croatia 3: Caballero drops clanger as Messi´s men are stunned|
|Funes Mori departs Everton to join Villarreal|
|Djokovic beats Dimitrov as Kyrgios lays down a marker|
|Relegated Verona appoint World Cup winner Grosso|
|Trotz named Islanders´ new coach|
|Matic and Serbia ready for ´hellish´ Switzerland clash|
|Fleetwood flounders as Gros takes Pulheim lead|
|No attacks on Neymar, pledges Costa Rica boss Ramirez|
|Giroud return brings structure to France, but again they disappoint|
|Brighton sign Sunderland goalkeeper Steele|
|Schmeichel and Eriksen blast ´exceptionally harsh´ VAR penalty|
|Nigeria´s young World Cup squad learning on the job - Rohr|
|Moody: England players need protection|
|France 1 Peru 0: Mbappe books last-16 spot with record goal|
|I don´t need anyone to hold my hand - Verstappen|
|Captaincy comes back around to Silva as 2014 pain fades|
|We don´t want to be losers - Petkovic|
|Alba not interested in Barcelona exit as Tottenham rumours swirl|
|BREAKING NEWS: Nagelsmann to take RB Leipzig role in 2019|
|Messi cannot be compared to Maradona, claims Argentina World Cup winner Kempes|
|Mbappe sets France record with maiden World Cup strike|
|Federer comes through tough Halle test|
|Nagelsmann to leave Hoffenheim amid RB Leipzig rumours|
|Gerrard brings former Liverpool team-mate Flanagan to Rangers|
|Cipriani to be ´the calmest guy in the room´ on England return|
|C´est magnifique! Lloris earns 100th France cap|
|Belgium v Tunisia: Hazard hoping for World Cup lift off|
|WATCH: Manchester United ditch piano to welcome Fred the red|
|Hamann springs to defence of Ozil|
|Alonso non-committal on future after Le Mans triumph|
|McInally returns to Scotland starting line-up|
|Giroud & Matuidi start as Deschamps drops Dembele for Peru|
|Torreira focused on Uruguay amid Arsenal links|
|NBA Mock Draft 2018: Deandre Ayton leads intriguing first round|
|Tite will not take away Neymar´s ´genius´|
|Australia show promise but calls for Cahill ignored amid lack of cutting edge|
|Manchester United means greatness - Fred aiming for titles following Old Trafford switch|
|Denmark 1 Australia 1: Jedinak strikes back after Eriksen rocket|
|Neymar not being put at risk by Brazil, says Tite|
|Juventus complete signing of free agent Emre Can|
|Fred completes Manchester United switch|
|Dembele will not join a Spurs rival|
|What were the 0.4 per cent doing? Iceland captain marvels at TV audience|
|Forsberg ready for ´next big step´ after RB Leipzig|
|´Retired´ Brits on bench as Springboks ring changes for final Test|
|Meninga: Key Kangaroos positions up for grabs in Origin|
|FIFA gets shirty over Ronaldo claims|
|Soyuncu keen on Arsenal switch|
|Atmosphere much better after criticism, says Hummels|
|FIFA issues statement after ´questionable´ Amrabat decision|
|Cipriani and Robshaw to start for England at Newlands|
|Team Sky hit back at Hinault´s ´irresponsible´ Froome comments|
|Iran fans are the real winners as women get glimpse of the future|
|Beckham predicts England-Argentina World Cup final|
|Napoli should sign Meret, Zenga claims|
|Meticulous Mouratoglou shaping stars of the future|
|Journalist hands Khedira boarding pass for early flight home|
|Germany v Sweden: Muller upbeat ahead of huge World Cup clash|
|South Korea v Mexico: Germany´s conquerors set for role reversal|
|Chandimal appeals against one-match ban|
|Fofana and Lamerat start, Parra skipper for final All Blacks Test|
|Asia and Africa being left behind - Queiroz|
|Emre Can arrives for Juventus medical|
|Championship fixtures: Bielsa´s Leeds face Stoke while Lampard´s Derby go to Reading|