Thursday saw the first leg of quarter-finals for both the Europa and Conference Leagues, with French teams Lyon drawing in London and Marseille settling for a 2-1 win on their home turf.
Torres’ equaliser makes them favourites for the return leg at Camp Nou next Thursday.
“We put in a superb performance and didn’t allow them much in the entire 90 minutes,” said Frankfurt scorer Knauff. “It’s almost a bit annoying that we didn’t hold on for the win, but anything is possible for the second leg.”
A sell-out home crowd of 48,000 created a highly charged atmosphere, inspiring Frankfurt to create 18 shots on goal, to Barcelona’s seven.
Barcelona equalised when substitutes Ousmane Dembele and De Jong combined before the latter teed-up Torres to fire home.
Frankfurt were reduced to 10 men for the final 12 minutes when Tuta picked up a second booking after a mistimed challenge on Pedri.
“It was difficult to get a grip on the game, they defended well and didn’t give us much space,” admitted Barcelona coach Xavi Hernandez.
“We were better in the second half, they attacked us on the counter and they had their chance. We will have our fans behind us for the return to hopefully put us in the semi-finals.”
Lyon draws with West Ham
Elsewhere, Jarrod Bowen scored as West Ham battled to a 1-1 draw at home to Lyon after Aaron Cresswell was sent off just before half-time for a foul on Moussa Dembele.
West Ham, playing in a European quarter-final for the first time in 41 years, went ahead in the 52nd minute when Bowen pounced on an error by Jerome Boateng.
Tanguy Ndombele, on loan from Tottenham, levelled for Lyon 14 minutes later.
“I thought the red card was cheap, if I’m really honest,” Bowen told BT Sport.
In Portugal, Abel Ruiz hit a fine goal in the 40th minute as Braga defeated Rangers 1-0.
An own-goal by Davide Zappacosta just before the hour mark allowed RB Leipzig to salvage a 1-1 draw at home to Atalanta.
Conference League: Bodo/Glimt beat Roma
In the Europa Conference League quarter-finals, Norwegians Bodo/Glimt grabbed a late 2-1 win over Roma on Thursday, while Leicester were held to a goalless draw by PSV Eindhoven.
Bodo/Glimt, who inflicted a stunning 6-1 defeat on Jose Mourinho’s Roma in the group stage, battled back from a goal down to beat the Italian giants again.
Leicester were the better side for long periods against PSV but will now face a tough test next week in the second leg in the Netherlands, after the two teams drew 0-0.
The Foxes are hoping to reach the semi-finals of a European competition for the first time in their history, after also reaching the last eight of the 2016/17 Champions League.
“There were not too many chances in the game,” Rodgers told BT Sport. “Maybe a bit more quality in the final third would have made it a bit easier for us. We just lacked that bit of quality up there.”
Feyenoord and Slavia Prague played out a thrilling 3-3 draw in Rotterdam, with Ibrahim Traore netting a 95th-minute equaliser for the Czechs.
Tear gas at Marseille
The winger set up Gerson to put OM in front in the 13th minute.
But there was better to come on the stroke of half-time, as Payet met Cengiz Under’s clever corner on the half-volley from 25 yards out, sending the ball flying into the top corner.
Moroccan Omar El Kaddouri pulled one back for PAOK early in the second half to leave the tie in the balance ahead of the return game, while Gerson was sent off in injury time.
“We wanted to win tonight,” Marseille midfielder Matteo Guendouzi told uefa.com.
“It’s a sixth straight win, we’re on a good run. We could have won by more but we’ll go there with confidence.”
The match was marred by some ugly clashes between supporters outside the stadium before kick-off with trouble continuing inside the ground.
Riot police fired tear gas in the direction of the Greek fans.
“In the second leg, I hope Marseille will be received as we have been received here,” PAOK coach Razvan Lucescu told a press conference.
“I am very disappointed with what I saw today, it is a very bad image for the city of Marseille. There is a lot of violence in the world today, there is no need to have it in football.”
(FRANCE 24 with AFP)