Arsenal needed a lucky own goal from a Granit Xhaka cross to salvage a point on the Atlantic Coast and stay on course for a Premier and Europa League double.
Mikel Arteta made six changes to his title favourites and saw stand-in keeper Matt Turner put in an unsteady display between the sticks for his disjointed team.
Sporting Lisbon fans started this rollercoaster last 16 tie with a rousing rendition of My Way and then watched their side fight back from an early William Saliba header to score twice - and striker Paulinho missed a great chance to give the brave Lions a 3-1 lead just after the hour. But moments later Xhaka’s cross took a massive deflection off Japanese midfielder Hidemasa Morita before finding the net to ensure this feisty tie will start all level at the Emirates Stadium next Thursday.
Yet Arsenal will be confident of going through as the Portuguese side, inspired by the former Tottenham winger Marcus Edwards, had a chance to decisive lead to London.
The Gunners also had chances. Gabriel Martinelli was denied a goal of a season contender when his storming run from his own half was stopped by a desperate late tackle by Dutch defender Jeremiah St Juste.
Poland defender Jakub Kiwior, who cost £17.6m in the January window, made his first appearance while Xhaka, Jorginho, Ben White and keeper Matt Turner all returned while Reiss Nelson was rewarded for his late Bournemouth winner with his first start since November. Gabriel Jesus did not travel. Hector Bellerin was denied a reunion with his former club after suffering a knee injury in a final training session on Wednesday.
But there were other former Premier League players on the pitch for Sporting.
Pedro Goncalves, who made one appearance for Wolves, had the first chance as he broke free down the left but curled his right foot shot wide. Former Liverpool and Sunderland defender Sebastian Coates then got involved and booked with Oleksandr Zinchenko after Saliba’s opening goal.
As the Frenchman headed home Fabio Vieira’s 22nd minute corner, the Ukrainian became entangled with Matheus Reis and started applauding when the Brazilian hit the ground. Uruguayan Coates stepped in and a melee ensued.
Turner, playing his first game since the FA Cup loss to Manchester City in January, made his first poor clearance with his feet before being at fault for the Sporting equaliser. Edwards swung in a corner and the USA World Cup keeper failed to come as Goncalo Inacio headed in from four yards out.
Turner made some amends with a fine stop from an Edwards shot.
A fitful first-half saw the best chances coming from set pieces or mistakes. Captain Xhaka hit the post from another Vieira corner while Turner again gifted the ball to Edwards only for the Enfield-born star and Paulinho to hesitate and the Arsenal keeper rescued the ball.
Arsenal seemed set to take control at the start of the second half as Martinelli forced a save from Sporting keeper Adan and Fabio Vieira shot wide. But after 55 minutes, Edwards slid a smart ball to Pedro Goncalves and when Turned blocked his shot, Paulinho fired home.
In a frenzied spell, Martinelli’s long-busting run just failed to provide an equaliser before Paulinho missed and Xhaka found the net via Morita with his speculative ball.
