If Virgil van Dijk is absent from the shortlists for this season’s Player of the Year awards, Celtic will surely fire off a stiff missive seeking clarification on the reasons. The prospect of a Treble evaporated last Sunday, an afternoon Ronny Deila now describes as the worst of his career. ‘I sat and stared at the walls,’ said the Norwegian of the aftermath. Eight points clear of Aberdeen with five games left to play, however, his outlook is suddenly brighter. Dundee's Simon Ferry (left) tussles for possession with Celtic's James Forrest (right) on Wednesday night . Celtic's Jason Denayer (left) challenges Greg Stewart (right) during the Scottish Premiership match . Dundee's Paul McGinn (left) and Celtic's James Forrest (right) battle for the ball at Den's Park on Wednesday . Dundee (4-4-2): Bain, McGinn, Konrad, McPake, Dyer, Ferry (Davidson 69), McAlister, Harris (Tankulic 59), McGinn, Stewart, Heffernan . Subs not used: Letheren, Clarkson, Black, Wighton, Colquhoun . Booked: Ferry, McPake . Scorers: McAlister 87 . Celtic (4-4-2): Gordon, Ambrose Emuobo, van Dijk, Denayer, Izaguirre (Tierney 81), Bitton, Brown, Forrest (Commons 76), Armstrong, Mackay-Steven, Griffiths (Guidetti 76) Subs not used: Stokes, Scepovic, Zaluska, Fisher . Scorers: Mackay-Steven 32, van Dijk 63 . Referee: Calum Murray . Attendance: 8, 908 . A fourth successive title looks to be a question of when and not if. It could even happen at Pittodrie on May 10, where van Dijk scored the most significant of his impressive 10-goal haul back in November. He was at it again last night, thrashing home his second 20-yard free-kick in as many games. Ever the perfectionist, his manager still wants more. ‘Virgil has shown that ability also last season with his free-kicks. We can also see it in training, so he has to use it more. ‘It became a very good night and we have put ourselves in a very good position. Eight points ahead with five games to go — and the goal difference as well. We just have to keep on performing and putting pressure on Aberdeen.’ Last Sunday, van Dijk’s early strike against Inverness was overtaken by events. Here, his thrashing effort past Dundee keeper Scott Bain earned Celtic the two-goal lead which ultimately repelled a late rally from the hosts. Jim McAlister’s goal in the 87th minute was too little, too late. Celtic's Gary Mackay-Steven (top) jumps over the challenge from Dundee's Willie Dyer (bottom) Celtic striker Leigh Griffiths (right) goes close with an effort on goal against Dundee on Wednesday night . Celtic had claimed the lead in 32 minutes and, with painful predictability, it was laced with more refereeing controversy. It was fairly mild stuff in contrast with Sunday — and the irony of Celtic being the beneficiaries here will be lost on no one. This is a week when Scottish referees are destined to be hoist by their own petard. A week when every error, minor or major, will be punished to the maximum. The row over the Josh Meekings’ hand-ball in the Scottish Cup semi-final defeat rumbles on but there will be no Parkhead postage stamps wasted this time. There will be no disputing the free-kick which teed up Gary Mackay-Steven’s superbly struck opener. Paul Hartley may have other ideas. ‘There were some decisions which I thought were quite bizarre,’ said the Dundee manager. ‘Referees are always under pressure but after what’s happened the last few days, the scrutiny is always going to be on them.’ It was Calum Murray’s turn to be placed in football’s equaivalent of a thumbscrew last night. A nondescript 32 minutes had passed without incident or urgency when a promising move by the visitors was interrupted by a barge on Mackay-Steven 30 yards from goal. It was a free-kick. Murray, rightly, played a good advantage before Leigh Griffiths immediately tripped over the ball and lost possession. The loss of the advantage was self-inflicted, yet to howls of derision from the home support, Murray pulled the play back for a Celtic free-kick. What came next was inevitable. Stuart Armstrong thumped a long ball towards the back post, van Dijk headed it firmly across the area and Mackay-Steven gathered on the edge of the box, rasping the ball into the top corner. Dundee’s sense of injustice was merely compounded by a penalty claim before half-time when Jason Denayer bumped into Greg Stewart. It wasn’t a penalty. Yet manager Hartley’s pursuit of the officials reflected a broader frustration with his team. Afterwards he bemoaned the lack of ‘cutting edge’ from his team. He wasn’t wrong. Stuart Armstrong (right) is challenged and sent hurtling to the ground by Dundee's Ferry at Den's Park . Mackay-Steven fires Celtic into the lead with a cool finish following a snaking run through the Dundee box . Against a Parkhead side missing Adam Matthews and Stefan Johansen, the Dark Blues struggled to make inroads until the late McAlister strike. Celtic were little better in the opening stages. The opening goal from Mackay-Steven relaxed them markedly. Griffiths was unable to turn the ball back into the net from an acute angle after Emilio Izaguirre’s cross was nodded across the face of the goal by James Forrest. The disputed free-kick changed things. With the lead they had cherished, Celtic seized the game by the scruff of the neck. They should have made it two in 43 minutes. Nir Bitton’s scuffed, mishit shot from the edge of the area fell kindly at the feet of Forrest in an onside position. The winger had time and opportunity to drive it home, but hit an unconvincing effort at just the right height for Bain to pluck the ball out of the air. Denayer’s clash with Stewart — a nondescript affair unworthy of a spot kick — provoked the ire and frustration of Hartley. Celtic had undeniably enjoyed a break from the referee for their first. There could be no real complaints over the free-kick which reaped their second in 63 minutes. James McPake clattered into Armstrong 20 yards from goal. It was the same proximity as last Sunday’s opener at Hampden — and the same devastating result. Like Ryan Esson for Inverness, the Dundee keeper had little or no chance of stopping the van Dijk free-kick which killed the game. The Dutchman stepped up and thrashed the ball into the top of the net. The game, to all intents and purposes, was done. Late on, Substitute Luka Tankulic miscued from close range after van Dijk made a hash of a downward defensive header, but McAlister finished in composed fashion with three minutes to play after Paul McGinn’s progress down the right flank ended in a low cross. Celtic survived. ‘It always becomes a little bit more nervy at the end,’ said a relieved, buoyant Deila, ‘but there weren’t too many chances. We were maybe a little bit naive, but we won the game and that was the most important thing.’ Griffiths is held off by Dundee's Thomas Konrad (right) during the Scottish Premiership match on Wednesday . Celtic defender Virgil van Dijk doubles Celtic's lead with a stunning free-kick against Dundee at Den's Park . Van Dijk is mobbed by his team-mates as they celebrate a 2-0 lead over Dundee at Den's Park .
Celtic beat Dundee 2-1 away at Den's Park on Wednesday night . The win sees them extend their lead at the top of the Scottish Premiership . Gary Mackay-Steven set the Bhoys on their way with a cool first-half finish . Virgil van Dijk scored a stunning free-kick in the second-half . Jim McAlister grabbed a late consolation for the home side on 87 minutes .