Kolasinac joined Arsenal on a free transfer from Schalke in the close-season and already looks an ideal fit for the Premier League.
Kolasinac joined Arsenal on a free transfer from Schalke in the close-season and already looks an ideal fit for the physical demands of the Premier League.
The 24-year-old came off the bench in the first half of Sunday's friendly against Chelsea at Wembley and won over his new team-mates with a commanding display, capped by Arsenal's 82nd-minute equaliser.
Kolasinac is usually a left-back, but he showed his versatility, replacing the injured Per Mertesacker at centre-back and helping the often leaky Gunners defence subdue Chelsea.
Not content with dominating at the back, Kolasinac popped up at the other end to score with a powerful header, forcing the penalty shoot-out that Arsenal won 4-1.
Walcott revealed the hulking Kolasinac has made a big impression with his no-holds-barred approach in training and the Gunners winger is expecting opposing forwards to get an even tougher time from the Bosnian this season.
"Sead looks an absolute tank. He is one tough unit to get past. His physical attributes are going to be key for us this season," Walcott said.
"He is an absolute animal. I see him in the gym everyday. You can just tell he looks after himself well. He eats the right foods. He is a professional."
"The power he's got and his pace, it's beautiful to watch. He's a great addition to the squad."
"Trust me, he is not easy to get around. He's quite wide as well. He fits perfectly for the Premier League."
"This league is the best and he's going to be one of the best in the league."
After last season's troubled campaign ended with FA Cup final victory against Chelsea, Arsene Wenger's side are under pressure to challenge for the Premier League title.
But, consigned to the Europa League after failing to qualify for the Champions League for the first time in 20 years, Walcott admits it won't be easy to change the perception that Arsenal have lost ground on their title rivals.
"It's going to be a tough season, we all know that, with the Europa as well," he said.
"We will let people talk on the outside. We know what we have to do this season."
"We know how important it is. We are up for the challenge, we do like a good challenge."
"It is going to be different this year. It's how we react. We can't really dwell on the past anymore."
"We have to focus on our strengths. We had a good end to last season and we are getting used to a new system."
"We are slowly learning it. It is working for now and we will stick with it."
Key to Arsenal's success will be the form of club record signing Alexandre Lacazette.
The France forward, signed for £46.5 million ($60.6 million) from Lyon, hit the post against Chelsea, but that was the highlight of a largely anonymous display.
Walcott defended his new team-mate, saying: "When you give him time and space on the ball he can show his quality."
"He's a goalscorer and he is going to score goals for this club."
"The amount of players we have in key positions, they are going to supply chances for him."
Arsenal open their Premier League campaign at home to Leicester City on Friday and Walcott can't wait to get going.
"Being a night game might be better for us. The fans will be up for it," he said.
"The home support is always crucial. That will be so key this season if the fans are right behind us from the kick-off."
"It's exciting. The Premier League is back. You are ask anyone, we are buzzing now."