I might be the dissenting vote here. It was only in the ground for a year, and it looks like it had a few losing matches with a weed whacker. Given that Aug - Sept is the best time of year to plant a mango tree (due to a combo of factors -- the mango's natural root growth cycle being in the fall combined with the fact that rainy season still has a couple of months left), if you can find a replacement tree, I'd plop one in the ground.
Certainly it will grow back, but you're not really gaining anything by leaving it (other than the price of a new tree).