Photo by Andrew Wevers/Getty ImagesJackson Koivun won a PGA Tour event in what was just his third start as a professional nine days ago at the 3M Open.Koivun is quite clearly a superstar in the making and at just 21, the golfing world is his oyster.The Auburn graduate has a certain level of maturity that belies his tender years, and if he continues to work hard, there is no doubt that he will go on to win many more PGA Tour events.Jackson Koivuns win at the 3M Open was made even more special by the fact that Scottie Scheffler was chasing him down on the back nine on Sunday.Photo by David Berding/Getty ImagesKoivun is unquestionably destined for the very top, and its clear to see that he is already very much ready to win.Perhaps the one thing that separates Koivun from the rest is the remarkably strong mentality that he possesses for someone so young.Jackson Koivun once revealed his number one goal in golfThe young man from San Jose, California, is incredibly ambitious, and why shouldnt he be, given his unbelievable talent?Speaking to the PGA Tours official website just before his first win, Koivun was asked to share his expectations for his first year on tour.Im trying not to put too many labels on it, the 21-year-old replied.I mean, obviously, to go out and win, would be great, but Im just trying to stay happy and enjoy it.Photo by Andrew Wevers/Getty ImagesJust kind of ease my way into it, and figure it out, and keep getting better and better, and see where I can get.However, his long-term goals are very clear.My end goal is to be the number one player in the world, Koivun admitted.I dont want to sound cocky in saying that, but I believe that if I just put in the work every day and keep getting better, I can definitely achieve that goal.Kevin Kisners word of warning for Jackson KoivunKevin Kisner spoke about Koivun on the Fore Play Podcast just after his win at the 3M Open last month.I dont love the straightening of both legs and his upper body having to bend over more. Obviously, its all patterns. Youve got to match. So if both his legs straighten, his upper body has to go down or youre just going to miss the ball, because youre changing levels. So theyve got to match each other, he said.I had a similar pattern earlier in my career. I had some lower back injuries, and actually worked a lot to change it, to try and get more into extension coming through it without straightening both legs.The pattern matches, because you straighten both legs, something else has to bend to make your circle hit the bottom in the right spot.Obviously, hes got it pretty nailed down, and I hate the idea of changing a 21-year-olds swing that just won on his third PGA Tour start as a pro, and being like, yeah man, your back might hurt in the future.So lets just wait until his back hurts, if it ever does, because he may just never have a back injury his whole career.