I think you need:
<?php
//check.php
if(isset($_POST["Insert"])) {
$player_name = mysqli_real_escape_string($tsrbase, $_POST["player_name"]);
$grad_year = mysqli_real_escape_string($tsrbase, $_POST["grad_year"]);
$query = "SELECT * FROM players WHERE player_name = '".$player_name."'AND grad_year = '".$grad_year."' ";
$result = mysqli_query($connect, $query);
if (mysqli_num_rows($result) == 0) {
$InsertQuery = new WA_MySQLi_Query($tsrbase);
$InsertQuery->Action = "insert";
$InsertQuery->Table = "players";
$InsertQuery->bindColumn("player_name", "s", "".((isset($_POST["player_name"]))?$_POST["player_name"]:"") ."", "WA_BLANK");
$InsertQuery->bindColumn("grad_year", "d", "".((isset($_POST["grad_year"]))?$_POST["grad_year"]:"") ."", "WA_ZERO");
$InsertQuery->saveInSession("WADA_Insert_players");
$InsertQuery->execute();
$InsertGoTo = "playersInsert.php?";
if (function_exists("rel2abs")) $InsertGoTo = $InsertGoTo?rel2abs($InsertGoTo,dirname(__FILE__)):"";
$InsertQuery->redirect($InsertGoTo);
}
}
?>