It may have been rude of Madrid's record goalscorer not to show his face, given Los Blancos were training at the facilities of his new team, Al Nassr.
The 37-year-old was nevertheless warmly received as his former team were put through their paces, training in the build-up to Sunday's trophy game against Barcelona.
Ronaldo watched the session and met with Madrid's players, the club said, with the Portuguese perhaps hankering for a slice of the action.
He also chatted with fellow former Madrid star Roberto Carlos, with the Brazilian making an appearance at the session as well.
Ronaldo last featured in a Supercopa for Madrid in August 2017, scoring in a 3-1 first-leg win against Barcelona at Camp Nou before Madrid won the second game 2-0 at Santiago Bernabeu to seal a 5-1 aggregate rout over its fiercest rival.
Ronaldo has yet to make his competitive debut for Al Nassr, which faces Al Shabab in the Saudi Pro League on Sunday (AEDT).
He is expected to miss that game, having also sat out a fixture against Al Tai last week, because of a two-match ban handed down by the English Football Association after Ronaldo slapped a mobile phone out of a young Everton fan's hand at the end of Manchester United's defeat at Goodison Park last April.
Ronaldo has signed a two-and-a-half-year contract with Al Nassr, the deal seemingly ending his long and successful career in European club football.
He scored 451 goals in 438 games for Madrid in a staggering nine-year stint with Los Blancos, before moving on to Juventus in July 2018.