The Johnnie Walker Championship was set to resume at Gleneagles on Thursday with Colsaerts in joint eighth place and in the hunt for the top-two finish that will give him a Ryder Cup debut next month.
But if the 29-year-old Belgian fails to achieve his goal he will be left hoping for a wild card, and that is where Harrington's opening 64 at The Barclays in America makes things interesting.
Assuming Ian Poulter is certain to be picked, it could be a battle between Colsaerts and Harrington for the other spot and, judging by what captain Jose Maria Olazabal said last night, Ireland's three-time major winner still has it all to do.
Two weeks after he commented that Harrington had to do something extraordinary to make the side Olazabal was asked what constituted extraordinary now.
"At least a win," he said.
It will make even more people think, rightly or wrongly, that the relationship between the two former team-mates has still not fully recovered from the incident at the 2003 Seve Trophy in Spain.
Olazabal felt his integrity was impugned when Harrington queried his repairing of a pitch mark on a green. He conceded the hole and at the end of the match they had a lengthy face-to-face by the 18th green.
Colsaerts, though, merely needs to focus on what he is doing.
"I can only be in control of what I do and worry about myself," he said after an opening 69 left him two behind leaders Brett Rumford and Knut Borsheim.
"I'll watch a bit (of The Barclays in New York), but it's not like I'm going to get crazy if somebody shoots 60.
"If I do good it should be good."
He is the only player in Scotland who can overtake Martin Kaymer, the man in the 10th and last automatic qualifying spot.
Kaymer is on a week off to Colsaerts' amazement, but Olazabal insists he will not hold it against the former world number one if he becomes the one requiring a wild card.
"I've always said that players are free to do whatever they want or whatever they think is best for them.
"I'm not going to force players to do something that they don't want to do. It won't count against him - I've always made that clear."