McDonnell couldn't find a yard of space in McCarthy's shadow, and the 21-year-old was pulled from the fray early in the second half of the drawn encounter.
Just a few weeks before, McDonnell was making a decent fist of being young footballer of the year. On a crisp Clones day, this unknown, slim slip of a lad proceeded to run amok on Gary Coleman, one of the most experienced campaigners around.
Unfortunately for the Derry veteran, his father was the only person watching not to notice.
McDonnell marked his first Ulster final appearance with a majestic goal, a wonderful curling point and a performance that threatened to take Kieran McGeeney's customary man of the match award.
Only for McCarthy to dent the fledging reputation. Two years is plenty of time for the dish to go cold, though, and if McDonnell wants revenge for the way McCarthy spoiled his first date on Jones Road, there is no better time than tomorrow.
In the intervening couple of years, McDonnell has become one of the most improved footballers in the country and he wasn't bad to begin with.
McCarthy faces a much better player tomorrow, one whose vast raw material has been harnessed to such an extent by Joe Kernan's magic, that he has all the tools to be the most impressive player in Croke Park.
Nigel Clancy knows all about
McDonnell's imperious form. He was full-back in a Sligo team that could be preparing for their first All- Ireland if the corner-forward hadn't scored six points in Navan six weeks ago.
McDonnell has impressed Clancy more than any other footballer this year.
"The style of play Armagh employ, the crisscross balls to their full forward line, it suits Steven down to the ground," he said.
"His fielding of balls is superb, there isn't a better forward at fielding balls, and he can pop up on either side of the square.
"In the last game, he gave Coman Goggins the run-around. And he is quick thinking, he is able to spot opportunities to create space for himself.
"Everyone knows he can score, but the chances he scores, they are down to his own creation, his own work. Peter Canavan is the only forward I have faced better at creating space for himself."
Although Joe Kernan is too well schooled in managerial diplomacy to say so, he must find time every evening to thank the Gods for McDonnell.
"When we have needed scores this year, Steven has come of age,"
Kernan says. "We have been labelled a negative team in some quarters, but Steven is one of the most positive players in the game.
"He is so comfortable on the ball and over the last three games, he hasn't wasted one pass in addition to getting some vital scores."
Gushing words on the eve of an All-Ireland final, but Kernan is wily enough not to say them if he didn't think McDonnell could cope with the pressure.
After his magnificent display against Sligo in the replay, people wondered would McDonnell string two impressive games together. Now that he has done, Armagh are asking for just one more.
McDonnell, who as a joiner is one of the few tradesmen on the field tomorrow, refuses to accept all the praise for the Orchard charge to the promised land.
"Nobody would be noticing me if the rest of the team weren't playing just as well because we wouldn't be winning. In the last three games, things have been going well for me, the ball has fallen right and hopefully, it will continue on Sunday," he says.
Whenever pundits have gathered to discuss the final this weekend, however, it has been the names of
McDonnell and Colm Cooper who have risen above others as match winners.
As Damien Barton said on End to End on Thursday night: "Steven has matured incredibly this year. He shows for the ball more than any other forward I have seen, and his fielding can be the difference between winning and losing a game."
A glittering memory from this year's championship was McDonnell's catch on the edge of the square, above three Dublin defenders, with the delicately poised game entering its final 10 minutes.
McDonnell has been a godsend for those who thought high fielding was a dying art in the full forward line. But, a point often neglected is how strong he is.
"He's deceptively powerful," says Clancy. "He is not a big corner-forward, but it is almost impossible to get the ball out of his hands.
"His passion is frightening for someone so young, playing in the full back line, watching him. He wants to win more than anything. Kerry will have to find a way to deal with McDonnell, if they want to win this All-Ireland."
Two years ago, when he teased Coleman for over an hour in Clones, McDonnell was considered a goal poacher. Since, he has added much more to his game. He can now strike points off either foot, and Kernan seems to have rid McDonnell of his tendency to drift in and out of games. As Clancy says, it is hard to see a weakness in his game at corner forward.
It is wondered what McDonnell recalls from his first tryst with Kerry in Croke Park. He winces at the memory, but answers the question.
"Well, in 2000, we went into that game with the Kerry full-back line thought to be a dodgy one. Seamus Moynihan and Mike McCarthy proved that year that they were unbelievable, they went on to win Allstars and those two are just as strong now as they were in 2000.
"And the line has only got stronger this year, with Marc Ó Sé coming in. He is just as good as his two brothers, and he is of the same calibre as Seamus and McCarthy, so you can't say there is a weakness in that line."
Tomorrow, Mike McCarthy will find McDonnell a significantly improved player since last they met in Croke Park.
He will also find someone burning with intensity and passion. As
Armagh's star forward says himself of the game: "It is every player's dream to play in an All-Ireland final. It is my dream to win one and this may be my only chance."