The two sites were suspended Monday night. (Screengrab)

Something strange happened Monday night, just as sports fans settled down to watch playoff baseball and “Monday Night Football” with their second screens as a companion for replays, snark and analysis.

Twitter accounts for two popular sports sites — @Deadspin and @SBNationGIF — were suddenly deactivated, rendering unavailable two of the higher profile sources for quick Vine, Periscope and GIF video replays of licensed, network broadcasts of games. (Vine is owned by Twitter.)

[Twitter suspends Deadspin and SBNationGIF accounts]

Some fans who post herky-jerky, oft-blurry clips also reported their Twitter accounts had been shut down. Those clips, most often, are the ones that are picked up by journalists, bloggers and fans, who then share them on their accounts, sending the users’ work viral.

So just who was to blame for trying to stop this now? The answer appears to be the NFL, UFC and the NCAA’s Big 12 and SEC conferences. Clearly, there were complaints under the Digital Media Copyright Act — and there may be more.

“Like all of our industry peers, we do not proactively monitor content,” Nu Wexler, a spokesman for Twitter, told the Post. “Rights holders report potential violations to us under the DMCA, we review their reports, and take action if the content violates our copyright policy.”

The NFL and UFC sent notices of violations of the DMCA to Twitter over what amounts to a microburst pirating of video of its games. Never mind that the popular clips drive viewers to find the games. Twitter shared with the Post two batches of DMCA complaints — 22 in all — related to the suspended accounts. There were 13 NFL complaints, primarily against Periscope and sites offering live-streaming of games, one UFC complaint against Deadspin for a tweet with video related to UFC 190 and four complaints by the Big 12 and four by the SEC, citing several instances of unauthorized GIFs.

“The NFL, as part of its copyright enforcement program, sends take-down notices to protect its valuable content from piracy,” NFL spokesman Brian McCarthy said. “Like other content holders, we acted appropriately to safeguard our intellectual property.

“In this case, we requested that Twitter disable links to more than a dozen pirated NFL game videos and highlights. It appears other content holders did the same.”

The decision for the NFL may have been rooted in a new multi-year deal it signed in August to bring real-time video highlights to users. Although the league had always shared highlights of top plays on Twitter, its account previously was slow, with video coming hours after the conclusion of games. 

This season, the NFL has considerably ramped up the effort to supply clear, clean clips of big plays in close to real time (with a sponsor’s ad at the top of each clip, of course). However, the simple fact is that the league can’t really keep up and that creates room for Internet users who aren’t watching with a corporate mentality. Most notably, @NFL may not agree with what is becoming a viral talking point of the moment. Von Miller is doing a “Key & Peele” sack dance of questionable taste? Don’t look for video of that from @NFL even if everyone is talking about it.

The NFL has long been vigilant about enforcing its copyright and trademark rights. Five years ago, when the New Orleans Saints were on their way to winning the Super Bowl, the league’s lawyers sent cease and desist orders to New Orleans businesses for printing and selling “Who Dat” shirts. “I really thought the ‘Who Dat’ was something that belonged to the people more than to the Saints or to the NFL or anything else,” shop owner Josh Harvey told WWL-TV.

NFL spokesman Dan Masonson explained then that “any unauthorized use of the Saints colors and other [marks] designed to create the illusion of an affiliation with the Saints is equally a violation of the Saints trademark rights because it allows a third party to ‘free ride’ by profiting from confusion of the team’s fans, who want to show support for the Saints.”

In Monday’s case of striking down clips, it isn’t clear at the moment just how much pressure was brought to bear on the NFL by its broadcast partners, the TV networks that collectively pay over $3 billion in rights fees to the league every season. An ESPN spokesman said the network had no involvement in the matter.

Deadspin, when its account was reactivated, opened fire on the easiest target, Commissioner Roger Goodell, even though the complaint that stopped Deadspin appeared to come from UFC. It was not immediately clear whether the NFL had filed similar complaints against the popular sports site. (As of mid-morning Tuesday, @SBNationGIF remained a suspended Twitter account, though the site issued a statement to the Post saying, in part, that the complaint was with college football content it posted. “We take copyright infringement issues seriously and always try to keep our use of unlicensed third party footage within the bounds of fair use,” the statement read.)

UFC has not responded to a request for comment, but it’s clear what its issue likely is: When the most popular fights — those involving Ronda Rousey — are over in less than a minute, the value of the pay-per-view is diluted. It’s unclear how many other leagues may get involved, but they surely are monitoring the situation.

“We’re constantly reviewing our rules and procedures. To the extent that they need to be adjusted, they will be, if we determine that that’s appropriate,” NHL spokeswoman Nirva Milord said in an email to the Post.

One league’s head honcho, however —  NBA Commissioner Adam Silver — is a contrarian, at least for now.

“Highlights,” Silver said with a shrug at the Sloan Sports Analytics Conference in February, “are marketing.”