IN some ways, this felt like a dress rehearsal of a potential play-off semi-final.

You had two of Sky Bet League One’s top six going toe-to-toe at a terrific tempo, with the noise bouncing around a near-capacity Home Park.

In a real play-off semi-final a 1-0 defeat in the away leg would not be a terrible result, but we saw why Oxford United still have work to do to get there.

Regardless of ability, you need a bit of luck and Karl Robinson rightly pointed to the game-changing moment that went against his side in the 34th minute.

It was more marginal than some are claiming, but Plymouth Argyle would have had no cause to complain if the offside flag had not gone up against Gavin Whyte and the penalty decision had stood.

Equally, United would already have been 1-0 up if the Northern Ireland international had been as clinical as he was for his country in Luxembourg last week.

It was a great save from Mike Cooper after nine minutes, but the home goalkeeper should have been helpless.

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The U’s did not have another chance so guilt-edged and you cannot pass up such a golden opportunity against a side who have now gone six games without conceding at Home Park.

It was another big moment in a match that was always likely to be decided by the odd goal, which came 11 minutes into the second half.

Joe Edwards’ volley was precise, but United's wing-backs may feel they could have done more.

Mark Sykes let Ryan Law inside too easily, allowing the Plymouth player to cross, while Ryan Williams could have been quicker to block the shot.

Both players have adapted excellently to their new roles since Robinson switched to 3-4-1-2 for the 4-0 win at Charlton Athletic on February 19.

Personally, I think it is a formation that brings out the best in United's defensive players. Luke McNally has the freedom to burst forward, Ciaron Brown seems most comfortable on the left of a back three and Sam Long was excellent again in the centre.

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Going forward is where the issues arise, not just in a midfield that can be overrun - although I thought Herbie Kane and Marcus McGuane did well at Home Park - but with the lack of two recognised strikers.

We were all drooling at how well Matty Taylor linked with Sam Baldock before the latter's injury and, while there is an understanding with Billy Bodin and Gavin Whyte, you surely need two goalscorers to maximise this system.

United were defensively sound until Argyle went ahead. It was the 50th league goal the U’s have conceded this season, the most in the top ten.

We know they can score, but they sorely need to improve on their tally of two clean sheets in 2022.

Another worrying trend is United’s growing tendency to fall away in the second half, which we saw last month against Ipswich Town, Shrewsbury Town and Portsmouth.

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Admittedly, the U's scored late in all those games, but their performance level also dropped and they threatened less than in the opening 45 minutes.

It happened again at Plymouth and a second goal for the hosts looked more likely than an equaliser.

United are out of the play-off positions with six games left, although a win at Morecambe on Tuesday would put them back in fifth. There is no need to panic.

That clash against a side in the relegation zone has to be a 'must-win', especially ahead of next weekend’s visit of sixth-placed Sunderland.