This is very unnecessary. I'm tempted to say that it's as unnecessary as possible. The entire sports section is already an open letter to sports people. To athletes, owners, fans, the whole lot. A sportswriter's principle job is to tell people how to play, coach, own teams, trade humans, behave on and off the field, cheer, boo, referee, umpire, officiate, celebrate, interview, ad nauseum. Tiger Woods is even told how to smile (use mouth) and sign autographs (more often, please).
Today, almost the only point of written sports journalism is commentary. Game summary is the property of TV sports anchors, guys who wear suits to talk sports and who keep them buttoned even when sitting down. Most act as if a mid-season Cards-Reds game were a meeting at Davos. They analyze routine plays with intricate graphics and earnest tones more appropriate for charting the Lower Dnieper Offensive. By the time a sportswriter gets his hands on the story, everyone who cares knows whether the game was won or lost, if the trade had been made, or that Chad Ochocinco celebrated a touchdown by taking a poo in the endzone. (Hey, one can dream.)
A football team has 11 players on the field at any given time. And that's just the offense. They need another 11 for defense. Loads, huh? Shut up and wait. I'm not through. They also got like 50 other guys who swap in and out for various chores (known as "plays") whenever the coaching staff feels like it.
Each team only has only one coach, but he has anywhere from 80 to 130 assistant coaches. Clearly, this is far too few people to figure out how to operate a football team.
Enter the sportswriter. He watches the game on Sunday just like everyone else, but with an eagle eye and an elephant memory. He might notice something that the coach, his staff, and the fans do not: that they punt too often or that the quarterback gets intercepted too frequently (which is bad) or that the running back only averages 2.1 yards a carry. Pretty good, right? That's higher than zero yards by a factor of 2.1. No, says the sportswriter. Multiply 2.1 by four downs, and you only get 8.4 yards per possession, which is not enough for a first down. (Roughly ten first downs are needed to make it from one end-zone to the other, depending on the stadium.)
Snap! says the coach reading the article on his tablet reader or smartphone. I did not notice my quarterback got picked off three times in the second half. He then makes the necessary changes and the team starts winning.
That kind of applied know-how is how a football writer uses inside baseball. Since the coach himself is already really into sports, (evidence: he does sports for a living), he probably reads the sports section. Sportswriters in general being a smart bunch, it is inevitable that one of them will inform the coach, through a commentary-heavy article, of his quarterback's heretofore unnoticed interception problem.
And thus, the open letter conceit is unnecessary. Even, perhaps, as unnecessary as humanly possible.