The fourth-and-15 alternative to the onside kick, which NFL owners are considering, is likely to be successful about as often as onside kicks were successful before the NFL changed the rules to make them more difficult.
From 2013 to 2017, the five seasons before revised kickoff rules made onside kicks harder, the success rate was of onside kicks was 16.3 percent.
In the 2019 season, NFL offenses that needed to gain 15 yards (running plays on third-and-15 or fourth-and-15) were successful 15.9 percent of the time.
So the alternative to the onside kick should work about 16 percent of the time, just as onside kicks worked about 16 percent of the time — until the NFL changed the rules.
Since the revised kickoff rules were implemented in 2018, onside kicks have been successful only 10.5 percent of the time. That’s not an enormous drop-off, but considering how vital the onside kick is to last-minute comebacks, there was concern in and around the NFL that they had become too hard to recover. The alternative will be a bit easier to convert, and comebacks will become a little more feasible.