Alan Smith concedes the season-ending injury to Theo Walcott will have major repercussions for Arsenal's title aspirations and England's World Cup hopes.
Walcott, 24, will miss the rest of the Premier League season and the World Cup in Brazil after suffering a cruciate knee ligament injury against Tottenham on Saturday.
And Smith, himself a former Arsenal and England forward, believes the loss of Walcott will push Arsene Wenger to be more active in the transfer market this January as well as forcing Roy Hodgson to rethink his World Cup plans.
Wenger was already looking for a striker this month, but the loss of Walcott - who operated as a central forward in the 2-0 victory over Spurs - has intensified Arsenal's need for a new forward.
"In that performance against Spurs at the weekend, when he played through the middle, he was a real threat and a real danger," Smith told Sky Sports.
"He gave Arsenal an option when they want to rest Olivier Giroud - he does need resting at times. So from that point of view it is a huge blow.
"Theo is now at the peak of his powers almost. He has had a period where he was learning the game and it looked uncertain whether he would actually make the top.
"But he has and his decision making is much better, and he is now a really mature player and a heck of an opponent for any defender with his pace.
"It is a massive blow for Arsenal and it might make Arsene Wenger a little bit more active in the January transfer window market. It is just what they didn't need."
Smith added that Walcott's injury will have huge ramifications for England as well.
Despite the rise of Tottenham's Andros Townsend this season, Smith says Walcott would have had a significant role to play in Hodgson's plans, especially with his electric pace.
"Andros Townsend has come into the England fold and done extremely well," Smith said.
"The problem for Roy Hodgson is that Andros is not in the Spurs team at the moment - that is not an ideal situation.
"But another Tottenham boy Aaron Lennon has come back into the side at White Hart Lane and started playing well. So there are one or two options but what you don't want to lose out of that side is pace.
"The way we might play at times in Brazil at the World Cup is on the counter attack, and in order to do that you do need the pace of the likes of Walcott. We have people like Townsend and [Daniel] Sturridge, who are very quick across the ground. But he would have been an option for Roy Hodgson."