Due to travel restrictions due to COVID-19, this match took place in Rome though the Portuguese side were the designated hosts.
Arsenal captain Pierre-Emerick Aubameyang should have given Arsenal the lead in a first half which finished goalless as he inexplicably shot wide when presented with a golden chance from close range.
Mikel Arteta's side looked like they could be made to pay for that miss when Benfica took the lead on 55 minutes after Pizzi converted a penalty awarded due to a handball from Arsenal's Emile Smith-Rowe.
But the visitors were level within two minutes as Saka converted from close range following a great ball from Cedric Soares.
Both sides appeared to settle for the draw with little attacking intent and few shots from either team of any note.
"I think we were very dominant we crated some big chances and in Europe when you have that away from home you have to be more ruthless. I think we could be in a much better position," Arteta said after the match.
Saka said he felt Arsenal had done enough to win the game. He told BT Sport: "We had a lot of chances. We dominated the whole game. They got a lucky penalty which I don't think was. We had to react well.
"We got a goal back and could have gone on to win it. It's not the worst result, we got an away goal. It was good inter-play [for the goal]. We managed to switch the ball and it was a good finish by myself so I'm happy with the goal.
"I feel like I'm improving every game. I'm trying to impress, trying to learn and listen to the boss because he gives great advice. I'm grateful to have a good team and good family around me. I just want to keep progressing.
"It is about managing the game. Last year when we went out to Olympiakos we conceded a silly goal. We can't put a foot wrong because if we do we will make it difficult for ourselves."
The return leg, in with Arsenal will be the home team, will take place in Athens on March 4.