Sixteen could be sour for Ospreys after thrilling win

Ospreys 17 Leicester Tigers 12: Full-back Byrne plays as extra man for a minute so hard-won last-eight place could be snatched away

These two teams always seem to produce a thriller and that thriller always seems to be steeped in controversy. Yesterday's humdinger was no exception; in fact it is already the most contentious of the lot. Everyone knows rugby union is a 15-man game but "for a significant part of the game" the Ospreys played with 16.

The Welsh region were celebrating qualifying for the Heineken Cup quarter-finals last night, as one of two best pool runners-up, thanks to Clermont Auvergne's win at Viadana, but they were doing so uncomfortable in the knowledge that Leicester will lodge a complaint which could, conceivably, see them effectively thrown out of the competition. Tournaments rules say the result of the match cannot be affected, but the Ospreys could be docked points.

In all probability, the worst they can expect is a fine. The precedents are in their favour. At the 2003 World Cup Dan Luger played for 30 seconds as the 16th man in a group game against Samoa – England were fined. In October, Nottingham lodged a complaint against Plymouth for having an extra man for a minute. The Championship club were cleared earlier this month. It is unlikely that would satisfy the Tigers.

Richard Cockerill, their head coach, entered the press room to say he did not want the Ospreys penalised – "as I don't think the result of the game was affected". But after looking at the tapes, his superiors seemed to hold a different view. Peter Wheeler, Leicester's chief executive, and Peter Tom, their chairman, arrived to announce that they would be taking the matter further, although they are not looking for Leicester to take the Ospreys' quarter-final place.

"During a significant part of the game, the Ospreys had 16 players on the pitch, and [the 16th, Lee Byrne] was involved in a break by Ben Youngs being stopped from developing," said Wheeler. "In the past teams have been strung up or had points docked for playing a non-registered player. By definition, the 16th man is not qualified to play. We think it affected the outcome of the game. The players put their heart and soul into it out there and they deserve to be treated fairly. What happens now is up to the ERC [European Rugby Cup]."

Tom said: "We don't want to seem like whinging, losing bastards, but this is a serious competition and a serious error has been made. We are 12 years or so into the professional game. People who administer the game have to make sure it doesn't happen again."

That would be the best thing to come out of a shambolic situation. The Ospreys claimed innocence but the bare facts are incontrovertible. Byrne went off with a bleeding toe in the 67th minute, to be replaced by Sonny Parker. Byrne re-entered the action in the 73rd minute – but nobody came off for almost a minute. And as Wheeler intimated, it was a fine time to have such reinforcements.

The referee, Alan Lewis, reacted with fury when he realised what was going on, coming to the touchline to remonstrate with the Ospreys camp and his officials. He was clearly not impressed and wanted to know who was responsible. Last night that was still unclear. Did the Ospreys send on Byrne without the permission of the line officials or was it the line officials' error? And should Lewis, as the rule-book states, have awarded a penalty to Leicester? To muddy the waters still further, there were claims that Ospreys players told Lewis that Leicester had 16 players on the pitch at that time as well. Of course, they did not.

The mess overshadowed a deserved Ospreys win and a, premature exit for the Tigers. The home side had built their lead with the boot of Dan Biggar and a try, just before half-time, by Tommy Bowe – a delightful kick from James Hook setting up the Irishman.

When the visiting scrum was destroyed on the hour, there appeared to be no way back. Yet, as so often, the Tigers launched a desperate finale. Notwithstanding "Stubbed Toegate", they had genuine opportunities to steal it. Scott Hamiliton came within a few yards and in the last minute Aaron Mauger knocked on with the whitewash a thrust away. The Ospreys held firm and as the only Welsh team left standing threw their arms up in delight, regardless of the fact that as runners-up they will face an away quarter-final. First they will have to survive the saga of the 16th man.

Ospreys L Byrne (S Parker, 67); T Bowe, A Bishop, J Hook, S Williams (N Walker, 79); D Biggar (Byrne, 73), R Januarie; P James, R Hibbard (E Shirvington, 76), A Jones, AW Jones, J Thomas (I Gough, 67), J Collins (F Tiatia, 76), R Jones (capt), M Holah.

Leicester Tigers S Hamilton; J Murphy (A Tuilagi, 55), D Hipkiss, J Staunton (A Mauger, 67), L Tuqiri; T Flood, B Youngs; M Ayerza (B Stankovich, 79), M Davies (G Chuter, 68), D Cole (M Castrogiovanni, 53), L Deacon (capt), G Parling, C Newby (B Kay, 61), J Crane, L Moody.

Referee: A Lewis (Ireland).