While it's not one of the PGA Tour's four major championships, The Memorial Tournament is still one of the top tournaments on the schedule, and a lot of the games premier players show up at Muirfield Village in hopes of winning Jack Nicklaus's tournament.
The two first round leaders for the The Memorial are Chris Riley and Rory McIlroy. The duo each carded a first-round 66 (-6) to take a one shot lead Chris DiMarco and Josh Teater.
Coming off a top-10 in this event a year ago, McIlroy continued his strong play at Muirfield. He carded seven birdies and just one bogey en route to his share of the first-round lead.
Riley managed eight birdies on his round, but was hindered by two bogeys. Riley is somewhat of a surprise first round leader. He comes into this event having scored just one top-10 finish in 13 events thus far this year, and he currently sits 141st in the FedEx Cup rankings.
Phil Mickelson, the fourth ranked player in the world had an up and down day in round one. He carded an even par round of 72 which saw three birdies, a bogey and an ugly double bogey on the second hole.
The round started off very strong for Mickelson as he birdied the 10th hole, which was his first hole of the day. After that he rattled off nine straight pars, before the double bogey.
Last week's PGA Tour winner, rookie Keegan Bradley, had a tough go of things in his first round as an official PGA Tour winner. He shot an opening-round 76, which has him 10 shots back of the lead.
He managed to card an eagle and three birdies, but found plenty of trouble with five bogeys and two double bogeys.
Defending Memorial winner Justin Rose began defense of his title with a first-round 71. He had four birdies and three bogeys.
Other notable scores include Rickie Fowler and Steve Stricker with four-under 68's. Matt Kuchar shot an opening-round 69. And reigning Players Champion, K.J. Choi and the new world No. 1 ranked player, Luke Donald, each opened with a round of 70.