Ten Hag demands Manchester United 'show resilience' in Europa League
The record 20-time English champions are off to their joint-worst start in the Premier League era, collecting just seven points from six games and scoring a mere five goals.
United also began their European campaign in worrying fashion, drawing 1-1 at Old Trafford last week with Ten Hag's former club Twente, a result midfielder Christian Eriksen said "feels like a loss."
It extended United's poor run in Europe to one win in nine games after last season's disastrous Champions League display.
Ten Hag again pleaded for more time to turn the club's fortunes around after the 3-0 loss to Spurs on Sunday, but the Dutchman admitted his team were far below the standards expected.
"We have to show resilience because this is not good enough. We have to accept this and, from this point on, we have to do things better," said Ten Hag.
"It is always a new day. I told them, just in the dressing room, to come on. Tomorrow is a new day. We definitely have to learn, we have to do things better.
"I just focus on Porto. We close this (Tottenham) game down, deal with it and then we move on. We will turn this around. We will start all over again. The season is still very young, with many games to play."
Ten Hag is waiting to discover the extent of injuries sustained by Kobbie Mainoo and Mason Mount.
United captain Bruno Fernandes, who grew up in Porto and played for local rivals Boavista in his youth, knows better than most what to expect from their upcoming opponents, beaten 3-2 by Norway's Bodo/Glimt in their opening game of the competition.
"It's a side that always does really well in Europe, we have to be aware of that," Fernandes told MUTV.
"(They are) improving a lot in the last few games, even if they lost the last game in the Europa League."
"We expect a really difficult game there, but we go there to win because it's everything that we have to think about," added the midfielder who avoided a three-match domestic ban after his club on Tuesday successfully appealed his red card in the Spurs defeat.
Spurs eye five in a row
Tottenham's convincing win over United was their fourth consecutive in all competitions and came without Son Heung-Min, sidelined by a hamstring issue picked up in the 3-0 victory over Qarabag when Spurs played almost the entire game a man down.
"Nothing changes," said manager Ange Postecoglou ahead of Thursday's trip to Hungarian side Ferencvaros.
"We've just got to keep doing what we're doing. There's still a lot of improvement to do in many areas, but the good thing about the group is they want to keep improving."
Rangers made a triumphant start away to Malmo and will host Lyon in their second game of the expanded league phase format. Lyon beat last season's Conference League winners Olympiacos 2-0 in their opening match.
Jose Mourinho's Fenerbahce visit Twente before United take on the man who led them to Europa League glory in 2017, after the international break.
Real Sociedad host Anderlecht and Ajax travel to Slavia Prague, while Lazio are at home to Nice. Roma try to continue their resurgence since the sacking of club icon Daniele De Rossi away to Swedish outfit Elfsborg.