NORTON, Mass. – Dustin Johnson could have used a finish like this for a record score. The birdie-eagle ending to his round Saturday at The Northern Trust gave him a 7-under 64 and stretched his lead to five shots in the FedEx Cup playoffs opener.Johnson, coming off a remarkable day in which he was 11 under through 11 holes and finished with seven pars for a 60, pulled away from Harris English and Scottie Scheffler with a 20-foot birdie putt on the 17th and a 40-footer for eagle on the closing hole at the TPC Boston.He was at 22-under 191, his lowest 54-hole score by three shots.“I'm in a great position and like where I’m at, but I’m still going to have to go out and shoot a good score,” Johnson said.