Phil Mickelson at British Open 2015: Sunday Leaderboard Score and Reaction

Phil Mickelson has had an up-and-down tournament at the British Open, and that didn't change Sunday, as Lefty shot a two-under 70, leaving him at four under for the tournament and needing a truly spectacular performance Monday to remain in contention for the title at St. Andrews in Fife, Scotland. 

He certainly felt as though he was on the precipice of playing better, as he told Alex Myers of Golf Digest after his third round:

Mickelson certainly got off to a shaky start, bogeying No. 1. But he quickly recovered, posting three birdies and five pars to close out a strong front nine. From there, he was steady, with pars on the next seven holes, before finishing his third round with a bogey on No. 17 and a par on No. 18.

For the day, Mickelson hit 69 percent of the fairways and 72 percent of the greens in regulation, averaged 289 yards on his drives and finished with 29 putts, per TheOpen.com. He also found himself looking up at quite a few players, however, heading into the final round.

Of course, if there is a player capable of exploding and posting an epic number Monday, it's Mickelson. While his play this year makes it tough to know what to expect—he has three top-five finishes, including a second-place showing at the Masters, but he's also missed three cuts and shot 13 over at the U.S. Open—he is the sort of streaky player who can erupt for an enormous round.

He might be lamenting the fact that he didn't play better Sunday, per Helen Ross of PGATour.com:

Of course, even if he does play out of his mind Monday, it may not be enough to catch a huge group of players lingering around the lead. With perfect conditions at St. Andrews on Sunday—at least perfect conditions for that particular course given the crazy weather of the past few days—more than a few players posted excellent scores in the third round.

Jason Sobel of ESPN humorously summed up the slew of low scores:

That means Mickelson will not only need to provide something truly special Monday, but he'll also need a good portion of the players in front of him to choke. And with a number of talented players in the running, that may be too big of a task.