Ronaldo's last Europa League game was in loss over Partizan Belgrade in 2002

It's been two decades since Cristiano Ronaldo last missed out on the Champions League.

The evergreen Manchester United forward, now 37, has accumulated 183 appearances across 19 seasons in Europe's premier competition, scoring 140 goals - both figures an all-time record.

Portuguese forward Ronaldo's figure of 140 is more than double everyone in history apart from four players - Lionel Messi (125), Robert Lewandowski, Karim Benzema (both 86) and Raul (71).

But after the Red Devils' hugely disappointing campaign in 2021-22, new boss Erik ten Hag and his side now face a return to the Europa League with a clash against Real Sociedad on Thursday.

If Ronaldo, who has been benched for the last four United games, plays a part in the fixture, it will be just the third appearance in Europe's second-tier competition across his long and illustrious career, and his first in 20 years, while at Sporting Lisbon.

But when were the last two and what happened in those games? Below, Sportsmail takes a trip down memory lane to recall the historic occasion...

Breaking through at Sporting

Laszlo Boloni, first-team manager at Sporting Clube de Portugal, AKA Sporting Lisbon, recognised Cristiano Ronaldo's potential straight away.

The Romanian elevated the teenager through the ranks, making him the first player to represent the club's Under-16, U17 and U18 sides, as well as the B team and first team, all in the same season.

Ronaldo only had one season of senior football with the Green and Whites before earning himself a move to Sir Alex Ferguson's Man United, where he was moulded into one of the best players in the world.

His Primeira Liga debut was on September 29, 2002 against Braga, and on October 7 he scored a double in a 3-0 win against Moreirense, putting him firmly on the radar of several top European clubs, including United, Arsenal and Liverpool.

Before his league bow, though, he was thrown into the first-team squad for two matches in the UEFA Cup, now known as the Europa League, arguably helping to launch his senior career.

What happened in the first leg?

Sporting were drawn against Serbian side Partizan Belgrade in the first round, and the first leg, in the Portuguese capital, saw Ronaldo named on the bench, with fellow skilful winger Ricardo Quaresma in the starting line-up.

Partizan took the lead on 11 minutes via a Hugo own goal, and although Tonito equalised, Andrija Delibasic put Partizan in front once again eight minutes before half-time. Boloni had seen enough.

At the interval, he made a double switch, bringing on widemen Ronaldo and Rodrigo Tello and taking off Pedro Barbosa and Rui Jorge. Ivica Iliev, however, scored in the 78th minute to give the visitors something to defend in Eastern Europe.

What happened in the second leg?

Ronaldo had obviously impressed enough to start the second leg - four days after his league debut - behind closed doors in the Serbian capital, and grainy YouTube footage shows flashes of the promise that alerted him to the likes of United.

A fresh-faced Ronaldo, in an odd-looking black kit with yellow sleeves and wearing No 28, received plenty of the ball from team-mates, who obviously trusted him despite his tender age.

The footage sees Ronaldo showcasing his now-trademark trickery, enticing defenders into fouls with mesmerising step-overs, feints and changes of pace.

He is brought crudely to ground several times by opposition players, but other than a brief moment of frustration, looking at referee Fritz Stuchlik of Austria with beseeching eyes, there is little of the whining now common to see.

In fact, after Tonito had helped Sporting take the lead, a nice bit of control saw Ronaldo cross for striker Vitali Kutuzov, who headed against the post before putting in the rebound to make it 2-0 on the night and 3-3 on aggregate.

After attempting a spectacular overhead kick and having a decent shout for a penalty turned down after being barged over in the penalty area by Milan Stojanoski, he was taken off on 74 minutes with Kutuzov for Marius Niculae and Barbosa.

Delibasic pulled one back but Pedro Contreras' goal made it 3-1 on the night, 3-3 overall, taking the game to extra time. With ten minutes until penalties, strikers Dejan Zivkovic and then Damir Cakar netted as Partizan progressed 6-4 on aggregate.

Ronaldo, however, had made his mark. United were calling.

Why did Ronaldo want to leave this summer?

The now-veteran superstar, despite scoring 24 goals in 38 appearances in all competitions last season, could not help United finish any higher than sixth, having been knocked out of the Champions League by Atletico Madrid in the round of 16.

Ronaldo made his position clear to the club and new manager Ten Hag: nothing but the Champions League was good enough, and United having failed to qualify, he wanted to leave.

But no concrete offers materialised: Saudi Arabian club Al Hilal were interested and made an 'obscene' contract offer but were never a realistic option, Chelsea owner Todd Boehly was keen but then-manager Thomas Tuchel turned the move down.

So after the transfer window closed earlier this month, it appears Ronaldo will be forced to stay at least until January, raising the prospect of another Europa League appearance 20 years after his first steps in the competition.

Thursday preview

Dropped after the club's 4-0 humbling against Brentford, Ronaldo now appears to be second-choice up front, with Marcus Rashford preferred after his resurgence amid Ten Hag's desire for pace, mobility and a pressing forward up top.

Ronaldo, therefore, short of match sharpness, could well be used to spearhead the United attack against Real Sociedad at Old Trafford on Thursday evening.

Imanol Alguacil's side have had a mixed start to the season and lie ninth in LaLiga after two wins, a draw and a loss from their opening four league games of the campaign.

They were humbled 4-1 at home against Spanish giants Barcelona and come up against another star-studded side, with United in fine form, on the back of four successive wins since the Brentford horror show.

The Basque club boast the likes of former Manchester City midfielder David Silva, winger Mikel Oyarzabal and striker Umar Sadiq in their ranks.

A far cry from the Partizan side of 2002, that's for sure...