No sooner has he been parachuted in as the president of the network's Europe, Middle East and Africa region, then two major names - Birds Eye and Bacardi Breezer - threaten to bale out.
No early trial of his leadership could be tougher than this. If he can galvanise McCann well enough to retain the accounts, he'll be hailed as a saviour. If he fails, there'll be no shortage of those savouring the schadenfreude.
Both pieces of business are crucial to McCann for different reasons. The Unilever-owned Birds Eye is a long-standing network client and will not have taken the decision to review its £22 million account lightly. Should it go, its departure will inevitably raise questions about McCann's ability to handle the complex and demanding international assignments that have been its forte.
Bacardi Breezer isn't in the same league. Nevertheless, it remains an important client which has allowed McCann to produce the kind of creative work which will make it more attractive to local clients who usually perceive it as an advertising factory whose structure and culture is best suited to multinational business.
With his experiences at the then HHCL & Partners to draw on, Howell knows only too well how the loss of a couple of accounts in rapid succession can make other clients nervous and precipitate a domino effect. Doubtless he will have been forewarned before his arrival about which accounts were in need of urgent care and attention and will have prepared himself accordingly. In his favour is the fact that he knows the culture of both the accounts very well. Not only is HHCL a Unilever roster agency but it used to handle Bacardi's Martini sister brand. However, such knowledge can work against you if the client is determined to break with the past.
Howell's priorities are obvious. First, he must seek assurances from the highest level at both client companies that McCann is being allowed to repitch on a level playing field and to be clear what the agency needs to do to keep both accounts. Second, he must understand the strategic challenges faced by both brands. Bacardi Breezer, in particular, seems unsure of where it's going. Above all, he must ensure McCann focuses on what needs to be done and rises above a "blame culture" - the inevitable by-product of so much internal upheaval. Retaining both accounts could be just the tonic McCann and Howell need.