Newcastle were denied a deserved three points as Liverpool rescued a point deep into added time at the Leazes End.
Isak could only manage a pained expression as he trudged off the pitch at St James’ Park, fully aware that his Newcastle teammates had been seconds away from securing their first Premier League victory under Matthias Jaissle.
The Sweden international had spurned a golden opportunity in front of goal amid jeers from the home supporters throughout the contest, yet it was Newcastle’s inability to clear their lines in the dying moments that cost them dearly.
The match seemed to be heading for a dramatic home triumph when substitute Joe Willock netted after coming on in the second period, only for the visitors to expose Newcastle’s defensive vulnerabilities once more in injury time.
Following a poignant tribute to Kevin Keegan that saw former club legends Tino Asprilla, Peter Beardsley, Lee Clark and Ruel Fox rise to their feet with emotion, the contest commenced.
Early on, Lewis Hall’s challenge on the visitors’ forward, who had been audibly greeted with disapproval since arriving at the stadium, established the match’s combative nature.
Newcastle took the lead through a strike Keegan would have admired. Debutant Amar Dedic nudged the ball into William Osula’s path, and the forward’s determined run, which involved six touches, ultimately set up Anthony Elanga.
The Sweden international then darted to the right flank before composing himself, taking a touch and rifling the ball into the far corner beyond Alisson at the Leazes End.
The goal unsettled Liverpool, though they crafted a clear opportunity in the 18th minute when Florian Wirtz struck low, only for Lukas Hornicek to deny him with a smart stop.
Osula threatened again on 25 minutes, yet Alisson blocked his effort, and a venomous free-kick from Dominik Szoboszlai, which Yoane Wissa had conceded to earn himself a booking, was impressively repelled by Malick Thiaw.
With 30 minutes gone, Harvey Barnes was brought down 25 yards from goal as Newcastle won a promising set-piece, with Osula’s initial effort striking the wall before his deflected follow-up resulted in a corner.
Lewis Miley picked up a caution for a challenge on Ryan Gravenberch, though Newcastle weathered the resulting free-kick.
Eddie Howe’s side continued to scrap and scrap in the remainder of the opening period and might have extended their advantage had Wissa done better on 44 minutes, but his attempt sailed wide.
After the interval, the first genuine opportunity for the home side fell to Miley, who lifted his effort over the crossbar as Newcastle searched for a crucial second.
Liverpool were equally profligate on 53 minutes when Cody Gakpo steered a right-footed attempt over the bar and into the Leazes End.
That served as a caution for Newcastle, with the equaliser arriving two minutes later, and it represented a frustrating goal to concede.
The visitors switched off in midfield, allowing Gakpo to enter the final third and curl a low strike past Hornicek to level at 1-1.
The goal prompted immediate alterations, with Osula and Sean Steuc removed before the hour mark, Jaissle sending on Jacob Ramsey and Joe Willock.
Willock had barely been on the pitch a moment, yet the midfielder formerly linked with a move abroad chose his moment perfectly.
First, Wissa muscled past two red shirts before driving through the centre and slipping in Willock, who had made an exhausting run down the left before bundling his way into the area and slotting into the far corner for 2-1.
Isak had a significant opportunity to silence the home supporters with 20 minutes remaining, but blasted over at the vital instant.
With 19 minutes left, Ramsey fired off target at the Gallowgate End as Newcastle again sought to increase their narrow cushion.
Jaissle turned to his substitutes with 14 minutes to go as Jacob Murphy and Aladji Bamba entered the fray for Miley and Elanga.
In the 86th minute, Wissa darted through once more on the counter-attack but Alisson conserved the 2-1 scoreline.
Shortly after, Liverpool substitute Victor Munoz, the Spain international who had rejected Newcastle previously, darted into the area but a superb sliding challenge from Botman thwarted him.
As Newcastle appeared to be heading towards three points, Lewis Hall’s challenge on Munoz was deemed sufficient for Stuart Attwell to award a penalty.
Despite vociferous home objections to what seemed a lenient call, the spot-kick stood with Hungary international Szoboszlai stepping forward to take it.
Szoboszlai placed it into the top left corner beyond Hornicek to draw the visitors level for virtually the final kick of the match.
Isak departed the pitch relieved, though upon reflection this may not be considered a poor outcome, with the application and performance evident for all.
Late goals in Newcastle versus Liverpool encounters have consistently proven dangerous, and once more that proved the case.