The job of running Microsoft’s flagging Google counter-offensive – which has lain like a fallow field since Kevin Johnson left the company in July to become CEO of Juniper Networks, having been foiled in buying Yahoo – has been filled.

As widely suspected lately, Microsoft is bringing in ex-Yahoo exec Dr. Qi (say Chee) Lu, who worked at Yahoo for 10 years.

The cost to Microsoft is ex-Aquantive CEO and current ad head Brian McAndrews, who having been denied the job, is picking up his toys and going home. Microsoft bought Aquantive in May of last year for $6.1 billion, its largest acquisition ever.

Lu, who was executive VP of engineering at Yahoo, responsible for search, advertising and e-commerce, before he left when Yahoo started snuggling up to Google, is supposed to start as president of Microsoft’s Online Service Group on January 5.

He will report to Microsoft CEO Steve Ballmer. Lu’s own reports will include Satya Nadella, head of Microsoft search, Yusuf Mehdi, who runs online audiences, and two new corporate VPs, unit finance chief Rik van der Kool, and Scott Howe, head of advertising and publishers now that McAndrews is going.

McAndrews will consult for a while. In a statement, Ballmer said, “While I am sorry to see Brian leave the company, I respect and understand his decision and wish him nothing but the best in the future.”

The Wall Street Journal observed that Lu could advance Microsoft’s case with Yahoo and make integration easier if it comes to that.