The Greeks were sent home from the European Championships on Friday night, but not before Samaras had become the first SPL player to score at a major international tournament since 2004.
For the record, the last player to achieve that feat was Henrik Larsson – then still technically a Celtic player but on his way out of the club – netted for Sweden.
Samaras's goal put the Greeks level with Germany, before Joachim Low's team went on the rampage, netting three goals in quick succession.
When Greece were awarded a spot-kick in the dying stages of the game, McGarvey wanted to see Samaras step up to take it, but instead it was Dimitris Salpingidis who took the honours.
Neil Lennon, though, will be hoping that once Samaras enjoys a break and then teams up with the rest of his Parkhead team-mates he will be boosted by his performances at the tournament.
And McGarvey, who has always been critical of the player's inconsistency, has told Samaras that if he wants to be considered one of the best at Celtic then he has to show that same heart and fight every week.
"It was a cracking goal that he scored against a side that could reasonably be expected to go on and win the European Championships," said the ex-Celtic and Liverpool striker.
"He showed great movement to get to the ball and even the presence of mind to make the run in the first place was good.
"I have never doubted the ability of Samaras – it just frustrates me that he doesn't play like that every time he pulls on a jersey.
"When he scored two goals at Ibrox 18 months ago and kick-started the title race, I felt sure that he would push on from there and go on to have a major impact on the remainder of the season.
"But it never materialised. If he does come back from the European Championships with a spring in his step then it is up to Neil Lennon to try and make sure that Samaras stays with it, that he doesn't drop off.
"There is obviously a lot of political upheaval in Greece just now. I felt as though Samaras had a bit of a point to prove against Germany, although he had rubbished that before the game.
"But he certainly played with a passion and a desire that we don't always see at Celtic."
The other aspect, of course, for Celtic is that Euro 2012 is a magnificent stage for players with the eyes of the world upon them.
Every player has his price tag and if an offer came in for the Greek international then Celtic's cause can be helped by the fact he had a reasonable showing in Poland and Ukraine this summer.
It is a sorry reflection on the current standard of the SPL that only Samaras and Mikael Lustig represented the league at the tournament, and while Lustig's involvement could have come at a substantial cost for Celtic – the player believes he may need an operation on a hip injury – Samaras did not too badly.
McGarvey said: "If he had scored the penalty which the Greeks got the other night I think that would have helped his case a lot; two goals at the European Championships is a fabulous return for any player.
"But I'm not too sure how much his value, if any, will have gone up.
"However, what it does do is bring him to people's attention. Celtic are in a nice position where they don't need to sell anyone and there is no pressure on them to balance the books that way, so they will be quite happy whatever happens."
Lennon summed up the divisive opinion on Samaras at Celtic's last AGM in October when he admitted the forward was the type of player who could get him the sack.
It is something that McGarvey concurs with and he has urged the player to sustain his performances over the course of a full season.
"Let's see what happens now," he said. "He should take heart from his goal and the fact he helped his country to get to the quarter-finals of the European Championships.
"It'll be interesting to see just where it goes next. It's up to the player himself to show everyone how good he can be."