The Giants have until March 4 to use their franchise tag and there’s a good chance they won’t designate any of their unrestricted free agents. Consider that in the 20 years since the franchise tag has existed, the Giants have used it only three times. No wonder co-owner John Mara said Tuesday what everyone already knew when he told the NFL Network the Giants “probably’’ won’t use the franchise tag on any player this year. Still, there are a few players who might warrant the tag. At the top of the list is Will Beatty, the soon-to-be 28-year-old left tackle coming off his first full season as a starter. For the first time, Beatty played in all 16 games, starting 15. The timing of this ascension was ideal for Beatty, a 2009 second-round pick out of UConn. He’s not at the level of an elite left tackle but he is athletic, an excellent pass protector and could be a fixture for years to come, as long as his back problems don’t flare up again. Beatty is a free agent the Giants must retain, one way or another, because there is no left tackle prospect on their roster and finding one elsewhere won’t be possible at any reasonable price. If the Giants cannot work out a long-term deal with Beatty, they can apply the franchise tag on him, which would guarantee him $9.66 million for the 2013 season. Any team interested in signing Beatty would have to negotiate an offer sheet and if the Giants did not match the contract that team would forfeit its next two first-round draft picks to the Giants. It’s a steep price no one will pay. The franchise tag would not be desirable for either side, however. Beatty, who made $800,000 last season, wants a long-term deal that will guarantee him much more than the franchise tag will pay. The Giants want to lock up their left tackle and they cannot afford him to count nearly $10 million on their 2013 salary cap. But the tag is an option to at least buy the Giants more time. It’s the tact they took last year when they designated punter Steve Weatherford with the franchise tag before coming to terms on a five-year deal. Beatty would be an attractive player on the open market. He’s rated as the No. 3 offensive tackle available by Pro Football Focus, behind Sebastian Vollmer of the Patriots and Jake Long of the Dolphins. Beatty played 967 snaps in 2012 and his only blemish was his 11 penalties, including eight for holding (six in pass protection, two in run blocking).