The Lions' head coach's men were comfortable 28-9 victors at Coca Cola Park on Saturday afternoon but it was the Springboks who finished the series as 2-1 winners.
That was after the Lions had come within a single score of a stunning first Test comeback and then been beaten at the death in the second rubber in Pretoria last weekend.
The margin of defeat in those Tests was just five and three points respectively and McGeechan feels it could well have been the Lions celebrating their first series victory in 12 years had a few minor things gone their way.
"We got a couple of 50/50s in this one," said McGeechan when talking about why the Lions had come out on top in Jo'burg but not at the ABSA Stadium or Loftus Versfeld.
"We've said all along that the games could have gone either way. We didn't have the breaks and we missed out on some things in the other Tests. We could have been 2-0 up or 1-1 but we were 2-0 down and that's how tight it's been.
"In the third Test, I thought we were very accurate in what we were doing and we were very intense. Tactically, we kept to how we wanted to play and we were very accurate in doing that."
Despite the disappointment of the series defeat, the most experienced coach in Lions history admitted that he and his fellow coaches would not have changed their tactics, approach or anything else in the build up to the series with the benefit of hindsight.
"There's absolutely nothing we would have done differently," added McGeechan.
"It's been a fantastic series. I have to say congratulations to the Springboks; they've won the series. We came out to win the series but they've won it and congratulations to them for that.
"That's international sport, and this is Test-match rugby - it's played on the edge."