Manchester United fans are hoping the club's newest star can inspire the team to victory in the Champions League.
Federico Macheda bagged a last-minute winner against Aston Villa on Sunday, and the 17-year-old is likely to play some part against Porto on Tuesday.
But he will probably start the quarter-final on the bench as Wayne Rooney - who was suspended for the match with Villa - is expected to return.
Arsenal are also in action on Tuesday, against Spanish side Villarreal.
But the English team are missing some important players, including top scorer Robin van Persie, and striker Eduardo.
Theo Walcott and Samir Nasri are both fit to play for the Gunners after being checked by doctors, but they may not be 100 per cent.
Arsenal captain Cesc Fabregas
Even so Arsenal will be hopeful of going through, and knocked the same opposition out of the competition in the semi-finals in 2006.
There was more good news for United fans following the Villa win, as Ronaldo said he was planning on staying at Old Trafford.
The Portuguese star was linked with a world record transfer to Real Madrid at the weekend, but on Monday Ronaldo said: "I am happy here. I think it is the right club."