TV measurement firm Nielsen has backed down from recent cable data after coming under pressure from ESPN. Fortune reports that the move comes after Nielsen released data late last week showing that ESPN had lost about 621,000 subscribers in a single month — which would have been the largest loss in the network’s history.

“Not only was the decline the largest ever, but it was more than twice as much as the average monthly decline ESPN has seen over the past few years,” Fortune notes. “And ESPN’s other sister networks, ESPN2 and ESPNU, lost similar amounts — suggesting that the network as a whole lost close to 2 million subscribers in October.”

The massive reported loss “led many to conclude that the danger posed by cord-cutting and other consumer behavior is accelerating, and pushing the sports giant off a rather large cliff,” Fortune notes.

ESPN was quick to bring the anomaly to Nielsen’s attention, and released a statement saying: “The Nielsen numbers represent a dramatic, unexplainable variation over prior months’ reporting, affecting all cable networks. We have raised this issue with Nielsen in light of their demonstrated failures over the years to accurately provide subscriber data. The data does not track our internal analysis nor does it take into account new DMVPD entrants into the market.”

Nielsen withdrew the report and announced that it is conducting an internal review.

In a statement, Nielsen said: “Nielsen is investigating a larger than usual change in the November 2016 Cable Network Coverage Area Household and Persons Universe Estimates (versus the prior month). We take the accuracy of our data very seriously and are conducting a thorough analysis to determine whether or not there is an issue with these estimates. We are working closely with our clients and will update them as soon as the analysis is complete.”