Ten Hag insists Onana is among Premier League's best goalkeepers
Onana's start to his United career has been riddled with high-profile errors in the Champions League that have put the Red Devils on the brink of a group-stage exit.
He was at fault as two Hakim Ziyech free-kicks kickstarted a Galatasaray fightback in a 3-3 draw in Istanbul on Wednesday.
That took United's tally of conceded goals in their five Champions League games to 14.
But it has been a different story in the Premier League as Onana has let in just 16 goals in 13 matches.
And Ten Hag pointed to figures which show the former Ajax stopper is second in the English top flight for saves made, save percentage and goals prevented.
"If you analyse it well then you see he is the second-best goalkeeper in the Premier League based on stats," Ten Hag, who championed Onana's signing from Inter Milan for £47 million in July, told a press conference on Friday.
"He's doing well. Also, he knows that in the Champions League he makes some mistakes, but all over you see the first five months he is doing particularly well."
United's Premier League revival after five wins in six games faces a stern test on Saturday as they travel to Newcastle.
But Ten Hag quashed any suggestion that Onana's place in the side is under threat.
"You have seen how he is reacting on a bad performance like in Munich. At Burnley (three days later) he was outstanding," added Ten Hag.
"He is a strong character, he is a personality and he will deal with it."
United's recent run has taken them above Newcastle in the table into sixth.
But all of their eight Premier League wins this season have come against sides in the bottom half of the table.
By contrast, they have lost all four meetings against teams in the top half.
Ten Hag recognised his players need to rise to the challenge when facing strong opposition.
"We have to rise to the occasion, be our best against them because the way they play is very organised," he said on the trip to Newcastle.
"I really respect them. It's a difficult team to play but it's a good challenge and I like to play against it."