Twelve cards were brandished by referee Niall Cullen in a stop-start affair, including a second red for Carlow midfielder Brendan Murphy in as many games and a black for Eoghan Ruth, while London also had Jarlath Branagan sent off for two bookable offences.
“I don’t know what to say about cards - we just have to look at that situation,” said O’Brien, who missed Murphy’s sending-off for a tussle with Owen Mulligan.
“It wasn’t a dirty game at all, it was played in a very sporting manner as I’d expect of the two teams. I just think the rules need to be tweaked because it is very difficult for referees and linesmen to make a call on these decisions and the difficult ones they have to make.”
O’Brien admitted his side were too cautious as they avenged their loss to London during this year’s National League. Carlow were ultra-defensive for large spells - even when playing with a strong breeze on their backs during the first half they stuck 14 men behind the ball.
The free-taking prowess of Paul Broderick and Darragh Foley got the visitors over the line, the former slotting six points, but this was not a game that will last long in the memory.
Carlow led 0-7 to 0-5 at the end of a forgettable first half thanks to three late points, Brendan Murphy grabbing the pick of those.
They had extended their lead to three points by the 42nd minute and London had goalkeeper Gavin McEvoy to thank for keeping them in the contest when he produced a fantastic point-blank save to deny Danny Moran.
The Exiles had Branagan harshly sent off moments later but Eoin Murray’s point from the sideline gave them hope, as did Murphy’s dismissal for grabbing Owen Mulligan around the neck.
Mulligan teed up London-born skipper Liam Gavaghan to make it a one-point game with five minutes remaining, but Broderick gave Carlow some breathing room with his sixth point and they played possession football in the closing stages to secure their second win of the summer.
“We are gutted, we are speechless because I think we put ourselves in a really good position to close out the game and nick that win,” said London manager Ciaran Deely.
“We had a certain amount of chances and the undoing of us really was probably conceding those scoreable frees in the second half.
“It’s very difficult for us because every year an Irish team comes over to Ruislip and we certainly don’t have an advantage of being at home and the referees certainly don’t help us in any situation.
“I find that difficult and I know the players find that difficult because I felt personally in the second half we were putting in some very good tackles back in the final third and we were being blown for the frees.
“That’s very frustrating for the players and for myself and the staff as well.”
P Broderick (0-6, 5 frees); D Foley (0-3, 2 frees); S Murphy, B Murphy, D O’Brien, J Murphy (0-1 each).
R Mason (freees), L Gavaghan (1 free) (0-4 each); E Murray (0-2); J Branagan, A Moyles (0-1 each).
R Molloy; C Crowley, S Redmond, C Lawlor; D Moran, D St Ledger, G Kelly; B Murphy, S Murphy; E Ruth, D Foley, A Kelly; P Broderick, S Gannon, J Murphy.
BJ Molloy for Lawlor (30), C Moran for Ruth (35, black card), D O’Brien for A Kelly (54), K Nolan for G Kelly (69).
G McEvoy; P Butler, Ciaran Dunne, C O’Neill; J Branagan, R Jones, Colin Dunne; M Carroll, C Og Greene; E Murray, L Gavaghan, M Gottsche; R Mason, O Mulligan, K Butler.
K Hughes for Carroll (ht), D Carrabine for Colin Dunne (ht), M McGirr for Jones (69), A Moyles for Murray (70), C Doran for O’Neill (70).
N Cullen (Fermanagh).