|Scottish Open first round leaderboard|
|-6||M Warren (Sco), K Broberg (Swe), R Gonzalez (Arg)|
|-5||J Rose (Eng)|
|-4||D Howell (Eng)|
|-3||L Bjerregaard (Den), M Ilonen (Fin)|
|Selected others||-2 L Donald (Eng), P Casey (Eng), G Hutcheon (Sco), -1 P Mickelson (US), Par R McIlroy (NI), D Clarke (NI)|
Rory McIlroy followed his course-record 64 with a 78 to fall back to level par after two rounds at the Scottish Open.
The Northern Irishman carded six bogeys and a double bogey for a seven-over-par round at Royal Aberdeen.
Scot Marc Warren shot 69 to share the lead on six under alongside Kristoffer Broberg and Ricardo Gonzalez, with Justin Rose (68) a shot further back.
McIlroy, 25, said: "It's been the case all year. I've got off to great starts and then fallen away."
After carding a 63 in the first round of The Memorial Tournament in Ohio in May he slumped to a 78 in the second round, but eventually finished with a share of 15th place.
McIlroy added: "I am still in the tournament and I can go out in the morning and try to get some of those shots back."
Defending champion Phil Mickelson (73) of the United States is on one under par.
Gonzalez looked certain to take lead outright overnight but he called a penalty on himself when he found bushes down the final fairway. He was leading by two shots but walked off with a double bogey on the 18th.
Joint leader Warren has a score to settle at this event, having let a three-shot lead slip on the closing holes at Castle Stuart in 2012.
|Rory McIlroy's 2014 implosions|
|Difference||1st/2nd round scores||Tournament|
|15 shots||63/78||The Memorial, May|
|14 shots||64/78||Scottish Open, July|
|7 shots||63/70||Desert Classic, January|
|7 shots||69/76||Wells Fargo, May|
|6 shots||71/77||The Masters, April|
"What happened two years ago was tough to swallow, but it was good experience, and I think in the future will stand me in good stead," he said.
Rose, who won the Quicken Loans National at Congressional last month, said: "I came here on Wednesday and felt absolutely horrendous. It was like I had lost my game somewhere over the Atlantic.
"But the last couple of days I have been finding my feet again and that's part of the reason for playing this week ahead of [The Open at] Hoylake."
Scot Russell Knox hit two eagles and a birdie in his first six holes but he struggled on the back nine and signed for a 74 to leave him level par.
Among the other home hopefuls is Greig Hutcheon, who is tied for 10th on two under after a second straight 70, with his countrymen Scott Jamieson (67), Stephen Gallacher (69) and Craig Lee (69) on one under.
Among those who missed the cut were English duo Lee Westwood, on three-over-par, and Ian Poulter, who finished five shots over par after two rounds.