<text>  Eight-time grand slam champion Andre Agassi believes American mens tennis has to regroup at grass roots level if it ever wants to boast a world number one again. The United States take on Great Britain in the Davis Cup in Glasgow this weekend, hoping to avenge last years 3-1 defeat in San Diego. World number five Andy Murray will lead the charge for Britain and goes into the first-round World Group tie as the stand-out singles player, with Americas John Isner and Donald Young ranked only 20th and 47th respectively. USA legend Andre Agassi pictured in 2009 says America must regroup its grass roots tennis set-up . World number five Andy Murray will lead the line for Great Britain at the Davis Cup this coming weekend . USAs Donald Young stretches to return a shot to Ivo Karlovic during the Delray Beach Open on February 22 . John Isner of the United States plays a backhand during his third-round match at the Australian Open 2015 . It is a far cry from the days of Agassi, who lifted the Davis Cup in 1990, 1992 and 1995 alongside the likes of seven-time Wimbledon champion Pete Sampras and four-time major winner Jim Courier. The last time America produced a male grand slam winner was 2003, when Agassi won the Australian Open and Andy Roddick triumphed in Flushing Meadows. Being the next Andy Roddick or the next Andre Agassi will still leave you shy of winning tournaments these days. Thats the truth, Agassi told Press Association Sport. Will we ever have a number one player again? Thats achievable, of course it is, but the four guys at the top now - Roger Federer, Rafael Nadal, Novak Djokovic and Andy Murray - they have redefined what this sport is all about over the last 10 years. You need something unique these days to make inroads, especially growing up in a country that doesnt have red clay courts. American tennis great Pete Sampras won the Wimbledon championship seven times during his career . Agassi has singled out Switzerlands Roger Federer as one of the four guys at the top now He has also placed Serbias Novak Djokovic on that list, pictured here at the Dubaio Duty Free Championships . Spains Rafael Nadal returns a ball against Argentine Juan Monaco during the final of the ATP Buenos Aires . I dont know where Andy spent his childhood playing he spent time in Spain as a teenager but he plays the game like he wasnt just playing indoors. We dont have that in America. We have a lot of fast court players and the ones who do shine are the ones who bring a different equation. Isner, for example, is a monster, hes 6ft 10 plus with a huge game, so we have to regroup at a grass roots level. Despite a shock defeat to 18-year-old Borna Coric in Dubai last week, Murray will be expected to win both his singles matches in Glasgow. That means the tie could depend on the doubles rubber, where Andy and Jamie Murray are set to face American twins Bob and Mike Bryan, the most successful duo of all time. American duo Bob left and Mike Bryan are set to come up against Great Britains Jamie and Andy Murray . Its a tough ask for both teams because theres very little that separates it, Agassi said. We have a big advantage in our doubles but you guys have a huge advantage with Murray. People think hes coming off a bad loss but Ive got news for you; hes going to be ready to go in a week and hes going to be playing his best tennis in front of a home crowd. I hope we can get over the finishing line and Ill have my fingers crossed like the rest of us. Agassi has previously admitted an interest in a coaching career and is even considered a potential mentor for Murray, who idolised the American as a junior. I enjoy the idea of coaching but I wouldnt physically, emotionally and mentally be able to do the job that I would want to do, Agassi said. You cant just step in and give advice. Coaching isnt talking, its learning. The things I say about Andy are not going to be a surprise to him. Its finding out what that switch is, its getting them to see something a different way and you cant do that until you spend time and learn with them. I cant commit the time now, even if I wanted to, I have too many responsibilities. That doesnt mean there wouldnt be a time in the future, but I cant do it at the moment. Agassi is tipping Murray to recover from his shock loss to Borna Coric and perform well at the Davis Cup . 