Plymouth Argyle were denied three points after a last-gasp equaliser from Adrian Mariappa rescued a draw for Burton Albion on Saturday. 

It was a frustrating afternoon for Plymouth who were hoping to get back to winning ways away from home when they took on lowly Burton.

However, Albion made it an uncomfortable afternoon for the League One leaders with several set pieces asking questions of Argyle throughout the game.

Steven Schumacher's side went into half-time a goal down thanks to a Bobby Kamwa goal four minutes before the interval.

Argyle's strong start to the second half was rewarded when substitute Ryan Hardie fired home from the penalty spot after fellow replacement Niall Ennis had been fouled by Hamer.

Ennis was then the architect of the visitors' second goal, with a slide-rule pass to pick out Bali Mumba, who finished unerringly into the top corner.

But just when Plymouth thought all three points were heading back to Devon, up popped Mariappa with his first Burton goal to salvage a deserved point. 

Here, we take a look at three things we learnt about Plymouth after their frustrating draw away at Burton.

Need to get back to keeping clean sheets

Surprisingly, Plymouth haven’t kept a clean sheet in their last six games and have conceded 13 in that time. 

It's a worrying trend for a team who were looking to be the runaway League One leaders this season and it perhaps highlights factors that need improving.

Burton were a constant threat from set pieces in this game with Schumacher needing his team to rediscover a mean streak defensively if they are to sustain a promotion challenge.

Bring Ryan Hardie back into the starting XI

Sam Cosgrove has been struggling lately and is goalless in his last six games in all competitions.

That left Ryan Hardie on the bench for the second consecutive game, and you could see the immediate uplift when he came on. His ability to make runs off defenders stretched Burton and asked several questions of them in his 30 minute spell. 

He is also a reliable source of goals for Argyle, so finding a way to unlock him consistently in games is perhaps a more successful route for the future than persisting with Cosgrove while he's out of form.

They need to improve their away form or risk dropping out the top two

Sustaining a promotion challenge means picking up more results away from home. Argyle are currently winless in their last three away league games and have conceded five in that time. 

Plymouth’s home form this season has been nothing short of spectacular. Argyle currently possess a perfect league record at Home Park as they have won all nine of the games that they have participated in.

It's unlikely that this will continue based purely on the law of averages, so improving away form will be a necessity for a successful automatic promotion challenge.