At the 15th, Mickelson botched a wedge, and he and Mahan each missed long par putts. Mickelson made a two-footer for bogey, but Mahan missed from three feet and made double-bogey.
Day, the 2011 US Open and Masters runner-up, missed a four-footer for par at the 18th and that left him with a final-round 71 in the clubhouse on 283, level with Mahan, but one back of Mickelson and two adrift of Rose.
Mahan took a bogey at 17 and only Mickelson could deny Rose from there, but instead, he found only heartache.
World No. 1 Tiger Woods fired a 74 to finish on 13-over 293 — his worst 72-hole US Open score over par as a professional — and shared 32nd place.
“It was a very good week overall,” Woods said. “I’m just sorry the golf was not where I would have liked it to be.”
Donald hit a woman with his tee shot at the third hole on his way to a bogey and was undone after that, with four more bogeys and a double-bogey on the rest of the front nine alone.
Stricker, who at 46 would have been the oldest champion in US Open history, went out of bounds off the second tee and shanked his approach on the way to a triple-bogey eight, a career worst one-hole score that helped doom his dream.