Already using its affiliated minor leagues to test the feasibility of robot umpires and bigger bases, Major League Baseball is now having one of its partnered independent circuits experiment with a tie-breaker that mimics the National Hockey League's shootout.

The Pioneer League, an eight-team association in the western United States, announced on the weekend that it will replace extra innings with a home-run derby to settle games tied at the end of nine innings.

The league's 96-game regular season opens on May 22 in Billings, Montana.

Under the new "knockout" rule, teams will select a hitter to face five pitches. Whoever hits more homers wins the game. A tie means a sudden-death round.

The Pioneer League will also introduce a "designated pinch hitter" (DPH) and "designated pinch runner" (DPR), which basically means teams are allowed to bring a player back into the game after he has been replaced by a pinch hitter or runner.

The DPH rule, which can only be used once by each team per game, permits a player not having previously entered into the game to pinch hit for an eligible roster player who may then return to his defensive position for the duration.

The DPR rule permits a player not having previously entered into the game to pinch run for an eligible roster player who may then return to his defensive position for the remainder of the game, until otherwise substituted for. The runner is thereafter ineligible to return to the game.

A revised check-swing rule has also been introduced, allowing hitters to appeal to the base umpire on check-swing strike decisions from the home-plate umpire. Previously, only the pitcher or catcher could ask for an appeal.

"I'm thrilled to see these exciting rules changes implemented for this season," Pioneer League president Michael Shapiro said in a media conference call.

"Our league is committed to developing ideas that enhance the strategy of the game, protect the safety of our players and add to the fun and engagement of our fans. We believe this focus will help ensure the future of baseball among a broader and more diverse audience."

The Atlantic League, another MLB Partner League, announced its own slate of rule changes earlier this month. The big one is moving the pitcher's mound back a foot (30 centimeters), which could theoretically cut down on strikeouts and help offense at a time in which balls in play are becoming increasingly less frequent at MLB level. The league is also trying out a rule in which teams are only allowed a designated hitter when their starting pitcher is still in the game.

MLB commissioner Rob Manfred has made no secret of his eagerness to change the game at the highest level to make it more viewer-friendly, and any or all of these changes could be adopted if they show promise in the minors.

MLB has been aggressive in recent years with rule changes, most notably the extra-inning runner rule being used this season and the universal designated hitter seen last year, which will likely return next season.