The Motherwell teenager rejected the contract offer made.
His decision saw the club tweet: "#CelticFC was pleased to agree a record-breaking fee with Motherwell FC for David Turnbull and we have quickly followed this up with a fantastic offer to the player through his agent.
"Currently, we have been unable to come to an agreement with the player’s agent. #CelticFC is content that it has made a magnificent offer and it is now up to the agent and player to decide if the player wants to join Celtic. If not, we move on."
It provoked a lot of reaction on social media with a mixed response from Celtic fans. Some saw it as embarrassing others were proud of their club for sticking it to the player and the agent in the open.
And, of course, supporters of other clubs spotted an opportunity to poke some fun at the eight-in-a-row Scottish champions.
@Jaicoybig_: "Think there's been a bit of s****housery going down with Motherwell going public and then the agent stuff and whoever leaked to the record today, the Celtic statement feels like a public dig about how it's been handled"
@ColmCeltic: "Fee agreed. Player turns down contract. Withdraw contract and move on. Club have done nothing wrong."
@NicolaMcCall11: "Always remember, the name on the back of the shirt is not bigger than the one on the front!!"
@christydon10: "Hello banter years"
@CollectCelticFC: "Quite right from Celtic. Great offer been made Nearly £3m to Motherwell who were out of order releasing details. Agent chasing a couple of Grand extra looks like has back fired. Enjoy Championship"
@garry_mclaren: "Well done Celtic for actually telling us fans what's happening . Turnbull has a chance to play at a massive club here and if he hits the heights he'll get a big money move to the premiership in years to come. If he turns this down then his agent is a clown, He is only 19."
@rawchicken17: "Shots fired at the agent"
@mclovespizza: '“If not, we move on” posted with all the resilience of some1 who sends the same DM to 20 girls at once. I love and respect it'
@LegalCheek_Tom: "Who the hell approved this statement?"
@CeltsAreHere: "Did you offer him a jacuzzi and/or Celtic pillow to sweeten the deal?"
@ScottAlcroft: "Is this how Club's are doing their transfer business now? On Twitter ffs?"
@SmallEd7: "I’m confident Celtic have made him a good offer, if he chooses to move to England for more money then he not wanting to play for Celtic and we move to players wanting to play for the club. Other areas need focus to help the squad and we have money to spend HH"
@SakurabaKS: '"Fantastic" offer. That doesn't sound like Lawwell'
@Andyfizz69: "Dodged a bullet, a bang average player, for £3 mil +, sort it out will you, a pub team player from Croatia would be better, again, tell neil he's the celtic manager,, not hibs"
@badgiebhoy: "Are we now conducting our transfer business via a running commentary on Twitter? Get this p**h aff of here and get this deal sorted!"
@TriviaTim: "He's obviously not signing now. Take the offer off the table and move on. Is it too hard to ask for a normal transfer window @CelticFC ?"
@ddoak93: "Wow very amateur from the club, if that's the case, are we now perusing a different approach to transfers and calling out agents for every player that knocks you back ? Not happy with the statement , too many getting made of late."
@frankgallaghe18: "For a business turning over £100M this is a disgraceful set of circumstances,the sooner the club can get someone in who can deal with these matters in a more professional manner, the better."
@pokeefe1: "Tinpot putting this out in public. Basically you couldn’t agree terms so far and are now stomping your feet. Embarrassing."
@aidxnUTLR: "We’ve gone from big club to tinpot in the space of a month. I’m not surprised we’ve done this not even a statement on the club website."
@ayremeraldcsc: "It's the right thing to do. Celtic set a transfer fee record with Motherwell and offer great terms. The agent wants more. Send a message out. Move onto the next target. Turnbull's choice Celtic, trophies, CL, career path Or Barnsley, relegation battle, no trophies Simple"
@RobbieSincIair: "You are the tackiest club in existence and lack even a shred of class"
@DagsJT: "Not sure how professional this is from @CelticFC to be honest. Deals and negotiations should be done in private and trying to bully the player into signing by going public is an odd move.
@CRH_Music: "Very rangers-esk this one. Straight of the Donald Trump book of doing deals. “Ye better get it signed or away ye get”. Should be better than this."
@conor_matchett: "I see Celtic have decided that it is time to break Rangers' streak for most ridiculous and astonishingly lacking in self-awareness club statement."
@sjc_101: '"I was going to dump you anyway"'
@FootballCliches: "Brendan Rodgers still has access to the Twitter account, I see"
@aHellofaBeating: "They’ve pinned the bloody tweet! Still time to delete and claim they’ve been hacked."
@GabyMcKay: "You know "magnificent offer" isn't too far from "concomitant risk"..."
@DuncMcKay: "Celtic FC are so small-time for such a big club. Enjoyable."
@euangtaylor: "You can tell it’s a good official club tweet when you have to check three times that it’s from the verified account before you allow yourself to laugh at it."
@KerryFail: "I’ve just spent half an hour updating my Celtic team on Football Manager, will Celtic refund the time? Doubt it."
@allymonc: "Have Celtic given Neil Lennon the social media gig as well as the manager's job?"
@mgm1809: "Well done Celtic who are these agents? could also say who is David Turnbull as have never heard of the boy before our approach"
@declan_r_m: "Cue another wasted career at some backwater English club on a salary only affordable via broadcast/parachute cash. At least the agent will be happy."
@shauncass: "Announce Jim Traynor"
@Wrighty0511: "This is an example of how NOT to conduct transfer business."
@Dogo2k: "This is so unprofessional. This can't be from the actual social media department at Celtic. We've been hacked."