Dubai, Oct 19 : Despite Australia opening batsman David Warner's form a huge concern ahead of their ICC T20 World Cup 'Super 12' opener against South Africa, all-rounder Glenn Maxwell has said that rivals should write off the stalwart at their "own peril". Warner's poor form has continued all season, with the Australian having an unforgettable Indian Premier League 2021 for Sunrisers Hyderabad, which was followed by a first-ball duck in the World Cup warm-up game against New Zealand on October 18. In fact, he lost his captaincy during the India leg of the IPL and was replaced by New Zealand's Kane Williamson, and during the UAE leg of the lucrative league, Warner was dropped for a few matches after string of poor scores. But Maxwell backed his long-time team-mate to return to form soon. "If you ever doubt Davey, it's an absolute no-no. You know he's going to turn it around. He's a superstar of all three formats. He's made so many runs. He's going to go down as one of the greats of the game. Unfortunately, he got Martin Guptill'd (caught Guptill bowled Southee) on Monday with an absolute hanger. Gup seems to do that a lot against us," Maxwell told espncricinfo. "Those sorts of things happen when you're searching for it. But you know when he gets out there come game time, come the 23rd (of October against South Africa), regardless of what happens in the next practice game, you know he's going to hit the ground running. He's going to be a big player for us." Maxwell also said that all-rounder Mitchell Marsh will have a huge impact in the tournament. "I think Mitchell Marsh is going to have a massive tournament. I don't think I've seen anyone hit the ball better, ever. We all gather around his net and just watch him hit the ball. It's been pretty extraordinary to watch him go about his business at the moment. I'd be really surprised if he didn't have a really good tournament. He's got his bowling as well. His presence around the group regardless of what he's doing is second to none. He's the guy everyone wants in their team, he's flying at the moment, so I'm expecting him to have a good tournament," added Maxwell. /IANS