CELTIC manager Brendan Rodgers cited a lack of quality up front as his side slumped to a 2-0 Scottish Premiership defeat at Dundee to leave them trailing leaders Hearts by five points.
A header from Clark Robertson and an own goal from Cameron Carter-Vickers gave the hosts a deserved half-time lead.
Despite the deficit, there was little in the way of a reaction after the break from the visitors, who managed just three shots on target.
Celtic upped the ante in the closing stages, keeper Jon McCracken tipping over an effort from Michel-Ange Balikwisha while the Hoops rightly had a penalty awarded for handball overturned.
By then, however, it was too little, too late and in truth, a goal would have flattered the visitors after a toothless performance.
The Dark Blues, despite only having two chances on goal themselves, deserved the win with their defence limiting Celtic to long-range efforts and half chances.
Hoops captain Callum McGregor tries to clear the pitch of tennis balls thrown by protesting Celtic fans shortly after kick-off (Image: Craig Williamson / SNS Group via Getty Images)Speaking after the game, Rodgers said the quality up front 'hasn't been to the level that we need'.
"I'm hugely disappointed and frustrated in the performance and the result," he told Celtic TV.
"Obviously, Dundee defended really well and got the goal from the set piece, that can happen.
"Sometimes you can get blocked off, it's a great delivery in, they get the header but still we didn't do enough with the ball when we had it.
"The second goal's a poor goal and from that we're then chasing the game at 2-0.
"The story today is the story of a lot of the season, six of the games we haven't scored in, so that always makes it a real challenge for you, especially playing against a team that are upping their game and are defending deep."
He added: "The quality at the top end of the pitch hasn't been to the level that we need and that's something that we have to continually focus on, it's as simple as that.
"We've dominated games, we've had opportunities, we could have had maybe a couple of goals today but if you don't have that killer instinct or you can't find that bit of finesse to get the goal, then it's a tough one."
Dundee's Clark Robertson celebrates after scoring to make it 1-0 (Image: Craig Foy / SNS Group via Getty Images)It may only be Celtic’s first domestic defeat of the season but that doesn't tell the whole story.
They have looked unconvincing since the start of the campaign, underscored by their tally of just 11 league goals.
At the same stage last season, they had scored 24, having won seven and drawn one of their opening eight games.
Results early in the season may have papered over the cracks, with Celtic having won four of their first five league games, drawing at Ibrox in the other outing.
However, they have now dropped five points from the last nine available and have managed only one win in their last five games in all competitions.
While the frailties may have been hinted at in the league, they were glaringly exposed in the Champions League.
Celtic failed to score in three-and-a-half hours of football over two legs and extra-time in their play-off tie with Kazakhstan's Kairat Almaty.
They then had three penalties saved in the shootout as they were dumped out of the competition by a side more than 250 places below them in UEFA's rankings.
They have so far managed a draw and a goal from their opening two Europa League games.
Problems on and off the field
Sunday saw a load of balls on the pitch at Dens Park — not the performance but a protest from Celtic fans that saw them throw tennis balls onto the pitch just after kick-off, delaying the action.
The club has faced criticism this season from fans over a perceived lack of ambition and activity in the summer transfer window and a failure to engage with fans.
That led to club officials meeting with representatives of fan groups earlier this month.
However, the Celtic Fans Collective said afterwards they felt 'the Club's leadership remains detached from the concerns of its supporters and reluctant to confront the need for change'.
A statement from the group this week announced the launch of the 'Not Another Penny' campaign, calling on fans to avoid buying club merchandise and match-day food and drink.
Some Celtic fans have started a 'Not Another Penny' campaign in protest at the way the club is being run (Image: Craig Williamson / SNS Group via Getty Images)The fans' concerns over a perceived dearth of quality in the squad were highlighted at Dens Park today, with forward Daizen Maeda missing out through injury.
Two summer arrivals — Michel-Ange Balikwisha and Marcelo Saracchi — as well as record signing Arne Engels started the game on the bench.
Of the four new faces to make the starting XI, two were free signings — Kieran Tierney and Kelechi Iheanacho.
The former Leicester man, as well as Balikwisha, Saracchi and Sebastian Tounekti, all arrived after that disastrous Champions League exit.
The club could argue that the players were signed with a revised budget in mind after missing out on the Champions League millions.
Conversely, supporters could argue it was a case of closing the stable door after the horse had bolted, making several late signings to appease fans when earlier and more ambitious transfer dealings could arguably have secured a place in the lucrative group stages.
Benjamin Nygren has made a solid start to his Celtic career, chipping in with four of Celtic's 11 league goals.
However, other notable signings have been conspicuous by their absence.
Shin Yamada has made one start and hasn't been seen since a second-half substitute appearance against Rangers in August.
Hayato Inamura has played just one game while Manchester City loanee Jamal Simpson-Pussey and highly-rated young forward Callum Osmand have yet to feature.
James Forrest was brought on at half-time to help try to overturn a 2-0 deficit (Image: Craig Foy / SNS Group via Getty Images)Perhaps summing up the squad issues best was Rodgers' half-time substitutions at Dens Park.
Trailing 2-0, he was left to turn to Irish striker Johnny Kenny, who has scored twice in 14 appearances, and 34-year-old winger James Forrest.
The one-club man has been a loyal, hardworking servant to Celtic but with his best years behind him, he is not the ideal option when trying to overturn a two-goal deficit.
Forrest is looking to extend a personal record, having scored in 16 consecutive seasons for the club but unfortunately for Celtic, he failed to do so today.
Instead, it was Dundee who rewrote the history books, recording their first win over Celtic in 24 years and a first home victory against the Hoops in 37 years.
With Austrian league leaders Sturm Graz in Glasgow for a Europa League tie on Thursday before a trip to Scottish Premiership leaders Hearts next Sunday, it's a crucial week ahead for Celtic.
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