Arsene Wenger expects forward Theo Walcott to make a full recovery from the cruciate knee ligament injury that will sideline him for six months and keep him out of the World Cup this summer.
Walcott, 24, suffered what at first seemed an innocuous injury in the final minutes of last Saturday's FA Cup win over arch-rivals Tottenham Hotspur at the Emirates Stadium.
Although he was carried away on a stretcher he was sitting up, grinning and gesturing Arsenal's 2-0 winning scoreline with his fingers as he was taken past angry Spurs fans who pelted him with coins. At that time, the injury seemed a minor one.
Wenger said on Friday it was a huge shock to hear about the extent of the injury on Monday.
"None of us expected such a bad injury straight after the game and it was devastating to hear on Monday night that he has got that problem," Wenger told a news conference.
"But Theo is very strong mentally and level-headed, and he is dealing with it as well as you can do when you are confronted with this kind of situation."
Asked if he thought if he would make a full recovery and keep his electrifying pace, Wenger remained optimistic.
"I am convinced that he will. Deep studies show that the players between around 25 with that kind of injury come back as normal. When you are over, 29, 30, you don't ever come back exactly the same."
Wenger also said he could not believe Walcott's bad luck regarding the World Cup.
He was included by Sven-Goran Eriksson for the 2006 finals as a 17-year-old to gain experince but never played, and was then surprisngly left out of the 2010 finals by Fabio Capello.
"It is unbelievable," Wenger said.
"When he was not ready to go he was selected and when he was ready to go he was not selected. Now nobody disputes he should go he is injured."
On a brighter note, the erudite Frenchman said he would have no hesitation in recalling his other England international forward Alex Oxlade-Chamberlain to the team if he was fit to face Aston Villa in the Premier League on Monday.
The 20-year-old winger injured his knee against Villa on the opening day of the season and has not played for the first team since but returned to action playing 45 minutes of a youth team match against Fulham this week.
Wenger said that forward Nicklas Bentner would not return until the end of January at the earliest and that he was keeping his options open in the January transfer window.
"We are open to possible solutions and if something interesting turns up we will do it," he said.