Sam Allardyce admits it was a "risk" to sign Jan Kirchhoff after the defender endured a debut to forget in Sunderland's 4-1 defeat at Tottenham.
The 25-year-old was signed from Bayern Munich during the week and came on at White Hart Lane with the scores level - but made several errors as Spurs came from behind to seal a 4-1 win.
Patrick van Aanholt had fired the Black Cats ahead only for Christian Eriksen to level for the hosts 91 seconds later and, with Sunderland on course for a point, Allardyce introduced Kirchhoff from the bench in place of Danny Graham.
Shortly afterwards Mousa Dembele arrowed in a second for Tottenham before Kirchhoff's token attempt at blocking an Eriksen shot from distance saw the ball loop up off his leg and past goalkeeper Jordan Pickford.
The defender's abject afternoon was compounded when he tripped Danny Rose in the penalty area to allow Harry Kane to sweep home the resulting spot-kick and Allardyce admits the former Germany Under-21 international needs time to adapt.
"There wasn't a lot he could do about the deflection," Allardyce - who missed his post-match press conference because of illness - told the BBC. "But the penalty, you don't hang a leg out there unless you're certain you'll win the ball. Hopefully he'll learn quickly.
"It's a bit risky signing players from abroad in January but we have to take that risk. Hopefully he learns from today.
"Our legs were running out and I wanted to make sure we had the energy to stay in the game. "John O'Shea and Wes Brown are in their late 30s so they will obviously feel the pace of the game. The extra defender was to tighten it up."
Allardyce, whose side remain in the bottom three as they battle against the drop, also hit out at his players for conceding so soon after getting in front at White Hart Lane.
"Our players put themselves in one fantastic position and then in the space of a minute conceded. It's one of the reasons we ended up losing," Allardyce added.
"If we came in at half-time 1-0 up we could have built on that. It was a really sloppy thing to do. We ran out of legs in the end."
Elaborating on the defeat in the post-match news conference, assistant boss Paul Bracewell echoed Allardyce's Kirchhoff assessment.
"He's learned what the Premier League is all about. It was a baptism of fire for him," Bracewell said.
"We've got to find out (how he will deal with it). He's learned it's a quick pace and there is no time to take chances in this league.
"Hopefully he will get over it quickly like all the players and we will work with them to make sure of that. It's been a tough week for all of them and I think the amount of travelling has affected them."