Ronaldo will miss Manchester United's final pre-season warm-up with a minor ankle knock but the Portuguese winger is expected to be fit for Sunday's Premier League opener with Reading.
Carlos Tevez and Gabriel Heinze also remained at home as Manchester United prepared to complete their final pre-season preparations in Scotland and Northern Ireland tonight.
With Tevez's registration not completed last night, Sir Alex Ferguson had little option other than to exclude the 23-year-old from the sides which travelled to Glentoran and Dunfermline respectively.
Instead the striker was expected to go through another training session at Carrington in the hope he will eventually be cleared to play some part in Sunday's Premier League opener against Reading.
Heinze was excluded from action too, having reported back for pre-season training with a slight muscle injury.
The Argentinian is unlikely to figure against Reading either, which means he will not play before the Premier League arbitration panel sit in judgement on his proposed move to Liverpool on Tuesday.
While the absence of Tevez and Heinze was anticipated, Ronaldo's failure to make the flight to Belfast robbed Glentoran of the undoubted star attraction of their 125th anniversary celebrations.
There was no immediate word from Old Trafford on the precise reason for Ronaldo's omission, although the Portugal winger completed the full 90 minutes at Wembley on Sunday without any apparent problem as United beat Chelsea on penalties in the Community Shield.
Ferguson, who has remained at home as well after being told by wife Cathy he must help out with a long-planned house move, did receive some good news though as Paul Scholes headed off for Dunfermline.
Scholes was expected to be missing for at least another week after flying home from the pre-season tour of the Far East to undergo minor knee surgery.
But the former England star would be in line for a place in Ferguson's squad at the weekend should he come through tonight's test at East End Park with no problem.
Joining Scholes at Dunfermline will be Wayne Rooney, Owen Hargreaves, Ryan Giggs and Scotland international Darren Fletcher.
Meanwhile, with no Ronaldo or Tevez to cheer, the Glentoran fans will have to satisfy themselves with England duo Rio Ferdinand and Michael Carrick, plus new arrivals Anderson and Nani.