Spain's Jon Rahm set the early clubhouse target as defending champion Rory McIlroy faced a lengthy wait to see if he would make the halfway cut in the Dell Technologies Championship.

Rahm carded six birdies and an eagle at TPC Boston to add a second round of 66 to his opening 67 and finish nine under par, two shots clear of England's Paul Casey and Canada's Adam Hadwin.

Americans Phil Mickelson and Grayson Murray were another shot back on six under, Mickelson shooting 67 and Murray carding a second consecutive 68 which included a hole-in-one on the eighth, his penultimate hole of the day.

Casey held a three-shot lead after 54 holes in this event last year, but struggled to a closing 73 and was overhauled by McIlroy, whose victory after a final round of 65 gave him the springboard to go on and win the overall FedEx Cup title.

The 40-year-old went on to finish second in the BMW Championship the following week and fourth in the Tour Championship in Atlanta, where McIlroy defeated Ryan Moore and Kevin Chappell in a play-off.

McIlroy has not tasted victory since after an injury-plagued season and faces a battle simply to qualify for the season-ending tournament at East Lake after a second round of 74 left him four over par.

That was one shot outside the projected cut and an early exit would see the four-time major winner drop to 49th in the FedEx Cup standings, with only the top 30 after the BMW Championship on September 17 qualifying for the Tour Championship.