Louis van Gaal said a “lucky” Luke Shaw only played in Manchester United’s penalty shoot-out win over Internazionale because Reece James was injured.

After Shaw had been branded “not fit enough” in the lead up the match, James was pencilled in to play but an injury meant Shaw took the field for the second half. The 19-year-old has been training alone and Van Gaal confirmed Shaw had been at FedExField earlier on Tuesday to try to improve his physical condition.

The manager said: “He is working very hard. He was lucky. Normally we would play Reece James but he was injured. So I asked Luke if he would play. He did a very hard training session this morning but he still did very good.”

Van Gaal also hinted he wants to buy two defenders following the departures of Nemanja Vidic, who played for Inter on the night, and Rio Ferdinand.

“We have conceded zero goals and then one wonder goal and a penalty. We are doing well but we are looking for defenders. Defenders have gone and we have to replace them. But I like [Tyler] Blackett and [Michael] Keane.”

Van Gaal would not be drawn on speculation that Javier Hernández’s future at the club is in the balance. “I can’t answer as he is a United player at the moment,” he said.

On Shinji Kagawa’s role as a No10 in the second half, the manager said: “I know him from Germany and he played No10 here. I want to play him in No6 or No8 in our system and I have tried that. I want to try him No10 because he wants to play there. He played better there than he did the other positions.”

Of his team’s performance Van Gaal added: “I’m pleased. We played better than our other games. We played well and conceded only one shot on goal. We created six or seven chances and that means it’s 7-1. I was very pleased with our ball possession. It was much better and we covered our positions better. I was very pleased with my players tonight.”

Wilfried Zaha impressed as a second half replacement in an unfamiliar role. “I was pleased. We have to see and wait. He has a lot of competition with the other strikers,” said Van Gaal.