William Saliba opened the scoring with a 22nd-minute header from Fábio Vieira's corner before Sporting scored a similar goal at the other end 12 minutes later as Gonçalo Inácio glanced home Marcus Edwards' delivery.
Paulinho gave the home side the lead 10 minutes after the restart before Gabriel Martinelli almost scored a sublime solo goal, dribbling from inside his own half and rounding Sporting goalkeeper Antonio Adan, only for Jeremiah St. Juste to make a last-ditch intervention. Arsenal restored parity on 62 minutes when Sporting CP's Hidemasa Morita suffered the misfortune of diverting Granit Xhaka's pass into his own net.
The second leg takes place next Thursday with Arsenal hoping they can secure their place in the quarterfinals for the fourth time in six seasons.
1. Arteta brings changes but Arsenal maintain push on two fronts
They required a couple of slices of luck -- none more so than their second equaliser ricocheting off Morita via a hopeful aggressive pass from Xhaka. But Arsenal will be confident of finishing the job in front of their own fans next week to reach the quarterfinals.
It would have been reasonable to think in August that the Europa League was one of Arsenal's best chances of success, but now that they have a five-point lead at the top of the Premier League, changes to the starting line-up were perhaps inevitable with Fulham to come in league play on Sunday.
Arsenal manager Mikel Arteta made six alterations here, partly informed by illness striking Martin Odegaard and Kieran Tierney while Leandro Trossard (groin) and Eddie Nketiah (ankle) also left back in London. And despite a flurry of excitement, Gabriel Jesus also did not travel as he nears a return from knee surgery.
Jakub Kiwior was handed his debut while Reiss Nelson came into the line-up after his last-minute heroics against Bournemouth at the weekend. There was inevitably a little less fluidity to Arsenal's play -- especially with so many key players, including Gabriel, Thomas Partey and Odegaard, not involved from kickoff -- and at 2-1 down, Paulinho missed a glorious chance to give the tie a completely different complexion.
But as it is, a draw with home advantage to come makes the Gunners favourites to reach the last eight.
2. Vieira performance a mixed bag, but one to build from
Vieira latest was simple enough: a corner swung onto the head of Saliba. The other opponents he has assists against -- Bodo/Glimt, Oxford United Wolves and Aston Villa -- are perhaps symptomatic of the limited opportunities he has had to impress so far.
On what was only his 12th start, Vieira was not able to dictate play with the same authority as Odegaard -- the player he was effectively replacing. He completed 31 of his 39 passes, but only 67% of those were in the final third.
Further improvement is needed but there are signs of encouragement for the 22-year-old to build on.
3. Set-pieces threaten to become an issue for Arsenal
The two first-half goals were very similar in construction -- a close-range header from a corner -- and it is not the first time Arsenal have looked vulnerable on set pieces in recent weeks.
It was the sixth goal they have conceded from dead-ball situations, seven if you count Bournemouth's kickoff routine that led to a goal in nine seconds last weekend. Manchester United, Everton, Brentford, Bournemouth and now Sporting have also benefited from Arsenal's weakness on set plays.
There were a series of individual errors in dealing with the 34th-minute corner from Sporting CP forward Marcus Edwards. Arsenal's Gabriel Martinelli allowed Gonçalo Inácio to escape his attention far too easily, Jakub Kiwior ducked under Edwards' delivery and Arsenal goalkeeper Matt Turner failed to command his six-yard box.
It is hardly worth panicking about Arsenal's set pieces at this stage, but after losing 1-0 at Everton to a goal from a corner, Sky Sports pundit Gary Neville said: "It did worry me a little bit, [Arsenal's] handling of set pieces, not just that but your handling of crosses into the box. Once other teams, analysts and coaches see a potential weakness, you are going to have to nip that in the bud."
The fact is, Arsenal haven't dealt with the problem and other teams are seemingly catching on.
Best and worst performers
Best: Marcus Edwards, Sporting CP
The former Spurs winger (although he never played for them) was involved in both goals and a regular menace to Arsenal's backline.
Best: Sebastián Coates, Sporting CP
Helped keep Arsenal at bay with some vital interceptions. Suspended after picking up a booking and will be missed.
Best: William Saliba, Arsenal
Scored the opening goal and recovered the ball eight times, providing a solid presence to help Kiwior on his debut.
Worst: Matt Turner, Arsenal
Made a couple of reasonable saves but looked shaky on more than one occasion and could arguably have shown more authority for Sporting's first goal.
Worst: Reiss Nelson, Arsenal
Failed to build on his stunning winner against Bournemouth.
Worst: Jakub Kiwior, Arsenal
Perhaps he received a call from Turner to leave the ball for Sporting's opening goal but it looked a bad error to the naked eye.
Highlights and notable moments
William Saliba opened the scoring in the 22nd minute on a close-range header.
Fábio Vieira earned the assist with a cross following a corner.
William Saliba rises highest to give Arsenal the lead. 💥 pic.twitter.com/g4jZTxHzGT— CBS Sports Golazo ⚽️ (@CBSSportsGolazo) March 9, 2023
About 12 minutes later, Sporting CP scored a similar goal of their own as Gonçalo Inácio headed it in from very close range.
It was assisted by Marcus Edwards with a cross following a corner.
Gonçalo Inácio draws Sporting level with a header of his own! 🇵🇹 pic.twitter.com/jgDvFtSdAn— CBS Sports Golazo ⚽️ (@CBSSportsGolazo) March 9, 2023
After the match: What the managers and players said
Arsenal manager Mikel Arteta on whether they were lucky to escape with a draw: "I don't know if we were lucky. Obviously, the second goal was lucky but Martinelli was through on goal and had a big chance. It's true that at 2-1, we conceded after a direct play and then lost a runner and they had a chance to make it 3-1. A lot of things to improve, that's for sure. But as well, we showed a lot of resilience to stay in the game, get back in the game and be alive in the tie."
Arteta on the team's performance: "Considering that we conceded two goals away from home and you still come away with a draw, you have to take some positives. I think we conceded two very poor goals, we gave them hope, especially with a lot of giveaways and simple balls that we lost in our own half. There were other moments where we had total control of the game and we looked a threat but lacked a little bit the capacity to punish them near the box. It's true that we are lacking four of our main attacking players. Overall, it's everything to play for and we have to play at the Emirates."
Arsenal's William Saliba on the result: "Today it wasn't an easy game but we scored the first goal and then they brought it back to 1-1 and then made it 2-1. As always we never give up and we scored the second goal. We have a game back home and we will give everything to win. We conceded two goals and the most important thing is that we didn't lose and we have another game."
Key stats (provided by ESPN Stats & Information research)
American goalkeeper Matt Turner earned his seventh start of the season for Arsenal across all competitions. He has kept a clean sheet four times.
Matt Turner recorded a -2.00 goals prevented against Sporting CP, his worst since joining Arsenal in June.
Sporting CP: Leões continue in the Portuguese Primeira Liga, hosting Boavista on Sunday, March 12. Then, Sporting CP continues in the Europa League with the second leg at Arsenal on Thursday, March 16.
Arsenal: The Gunners resume Premier League play by visiting Fulham on Sunday, March 12. Then, Arsenal host Sporting CP in the Europa League return leg on Thursday, March 16.