Mr. Carroll, who had been TBWA's president-CEO since 2007, was named chairman of TBWA Group, which includes TBWA and the other Omnicom agencies that report to it. Jean-Marie Dru continues as chairman of TBWA Agency Network, which consists of agencies using the TBWA moniker around the world.
Executives in adland have been watching executives such as Mr. Ruhanen and Mr. Carroll at Omnicom as well as Publicis Groupe, speculating about which would remain in their current positions after the two holding-company giants' spectacular failure to merge this year.
Mr. Ruhanen, a veteran at TBWA sibling BBDO, was tapped for the Omnicom role last October, assigned to drive collaboration across agencies for the group's largest accounts. His name surfaced recently as a likely candidate to succeed Mr. Carroll, partly given his involvement with massive Omnicom global clients like AT&T, McDonald's and Apple. TBWA and Omnicom have been striving in the last year or so to improve the relationship with Apple in particular.
"Under the leadership of Tom Carroll, TBWA is recognized worldwide for its strong culture and award-winning creativity," said Omnicom president-CEO John Wren. "At Omnicom, we place considerable emphasis on succession planning, and Tom and I have long agreed that Troy Ruhanen would be the right person to take the helm of TBWA. His experience in leading Omnicom agencies across geographies and categories makes this a seamless leadership transition that will build upon TBWA's capabilities and reputation as one of the best in the business."
Prior to his holding-company role, Mr. Ruhanen was chairman-CEO of the Americas for BBDO. The Australian originally joined BBDO's flagship New York office from Leo Burnett in 2004, and quickly rose to oversee the agency's biggest region.
Mr. Ruhanen's appointment comes just as TBWA has been eliminated from a review to keep the global Infiniti account. (That review, which is said to be completed in August, is being handled by Roth Observatory.) TBWA, as part of an Omnicom agency solution dubbed Nissan United, also works on auto-sibling Nissan, which is not in review.
But TBWA has faced a protracted defection of global accounts in recent years. Its global Beiersdorf business went to Interpublic's FCB in 2010, Mars in 2011 consolidated creative for its brands at BBDO and DDB, and Visa shifted its global account back to BBDO from TBWA in September 2012.
The global leadership change also comes less than three months after TBWA Los Angeles, a crucial office in the network and a onetime creative powerhouse, shuffled the upper ranks to facilitate a turnaround. In April, it named Luis DeAnda president of TBWA/Chiat/Day's Los Angeles office, succeeding Carisa Bianchi, who left the shop after 24 years. Mr. DeAnda had been with the TBWA network for 12 years, joining TBWA in January as managing director after serving as managing director at TBWA/Media Arts Lab, where the network's Apple account is housed.
A few weeks later TBWA Los Angeles promoted one of its executive creative directors, Stephen Butler, to chief creative officer, a post that had been vacant since John Norman left for Translation in February.
The L.A. office also split with Crate & Barrel this year and has seen its work for PepsiCo's eponymous soda brand defect to a host of other agencies, albeit also to Omnicom's Galaxy group, which includes TBWA. The shop still handles PepsiCola's Gatorade.
TBWA in London this year picked up the account for global auction house Sotheby's and handles a chunk of McDonald's work globally.
Mr. Carroll began his career in 1978 at Mathieu, Gerfen and Bresner, and eventually landed at Chiat/Day -- a moniker that is now tacked onto TBWA's U.S. offices. He left in 1989 to co-found Weiss, Whitten, Carroll, Stagliano but returned to TBWA in 1999 to run its Los Angeles office. Two years later he was named president of the Americas and in 2004 he was named worldwide vice chairman.