Callum Robinson struck 11 minutes from time to deny Millwall a fifth win in their last six Championship home games.

The Lions had taken the lead on the stroke of half-time through Aiden O’Brien, but Robinson chested home from a few yards to deny the Lions all three points.

Here are five things we learned...

Millwall’s small squad is clear to see

Millwall have used fewer players than any other Championship club this season (21) and their lack of squad depth is beginning to take its toll. Neil Harris opted against bringing on Tom Elliott against Preston, who clearly isn’t fully fit yet and the amount of games Lee Gregory and Steve Morison are being forced to start is really starting to show. Harris stated post-match that he isn’t close to bringing any players in, but is still working on two loan deals and a striker should really be top of his wish list.

More points dropped from a winning position

It’s now 16 points dropped from winning positions and if the Lions had claimed half of those they would be within touching distance of the play-offs. They have taken the lead against Bolton, Ipswich, QPR, Sunderland, Wolves, Norwich and Preston and failed to win any of them, taking just five points from those seven games.

The unbeaten run at the Den continues

Millwall are on their best Championship home run since December 2013 having not tasted defeat at the Den since Burton Albion’s 1-0 win in November. Harris’ side have taken 25 points from a possible 42 at home, giving them the eighth best record in the Championship and the draw with Preston means that none of the current top ten have left the Den with three-points.

O’Brien’s revival continues

It had been 18 games without a goal before O’Brien scored twice in last weekend's win over Barnsley in the FA Cup and the way he swept home on 43 minutes against Preston was the sign of a man playing with confidence. Gregory’s attempt to turn home Jed Wallace’s near-post cross could have easily distracted O’Brien but it didn’t seem to affect him as coolly slotted home to put Millwall ahead just before half-time. Only George Saville has scored more goals that him this season (7).

More poor refereeing cost the Lions

Not for the first time this season, Millwall were on the receiving end of a controversial refereeing decision that infuriated Harris. Preston midfielder Ben Pearson was already on a booking when he fouled Wallace midway through the second-half and despite appeals from the Lions' players, nothing was given. Gregory was then denied his fourth goal of the season as he was flagged for offside just after he slotted home when replays suggested differently.