Howard Katz, the titular tyrant of Patrick Marber’s surprisingly facile new morality play, typically doesn’t hold on to assistants long enough to impart much in the way of wisdom. But the blustery London talent agent does warn one new hire about the perils of thinking too much: “In this business, if someone says to you that they will ‘think about it,’ their answer will be ‘No.’ That which requires our thought is undesirable.”

Howard Katz practices what he preaches in “Howard Katz,” Mr. Marber’s hard-charging amalgam of “Jerry Maguire” and Arthur Miller’s “After the Fall,” with a generous dollop of showbiz rubbernecking tossed in. A goateed pit bull of a man who swings at unseen assailants in his sleep, Howard (Alfred Molina) plows through life with an almost feral single-mindedness. His idea of relaxation is fantasizing about playing Russian roulette; his idea of parenting is urging his 10-year-old son to kick a bully in the groin and then spit on him.

Mr. Marber, whose first two plays anatomized the lacerating effects of deception within father-son relationships (the underrated “Dealer’s Choice”) and among the London culturati (“Closer”), blends those two themes here. Intact are the hostile witticisms and ferocious jockeying for psychological supremacy. What’s missing, though, is the hard-earned complexity that comes from watching formidable characters match wits. “Howard Katz” is either a one-man show with too many other characters or an ensemble drama with too few.

It isn’t giving anything away to say that Howard’s success proves short-lived; the play begins with him sprawled out on a park bench, wiping his brow with a rumpled yarmulke and handing over his wallet to a seedy hustler named Robin (Euan Morton). The only real questions facing the audience are: How did he sink so far, andis he going to bounce back or slide away altogether? (Even here, Mr. Marber’s gift for cutting wit remains intact: “Don’t do it, mate,” Robin advises at the suggestion of suicide. “You might regret it.”)

The rest of “Howard Katz” is devoted to answering the question of Howard’s implosion through a lengthy flashback. Mr. Marber and director Doug Hughes, however, gloss over several of what appear to be the most crucial moments. And the whole “to be or not to be” issue? (Howard clutches a dingy plastic bag that contains, among other things, a straight razor and a bottle of pills.) Unlike theater’s most famous suicide risk, Howard is being assailed by boomerangs instead of slings and arrows; his sea of troubles is almost entirely of his own devising. Howard hits his kid and ignores his wife. Cut to Howard sleeping in a flophouse. Howard demolishes three office phones in a week. Cut to Howard begging for his job back, suffering something close to a psychotic break in the process.

Unfortunately, these reversals of fortune, while believable in theory and depicted effectively by Christopher Akerlind’s scene-shifting lighting design, flash by too quickly to succeed dramatically. For all the quotable barbs, Messrs. Marber and Hughes offer little in the way of plausible relationships to counter Mr. Molina’s relentless physicality, with his impassive midsection and his fidgety arms and legs. “Everyone reminds me of everyone else,” a newly reflective Howard confesses near the end. This inability to individuate, not the workplace tirades or the neglect or the abandonment of Judaism, is Howard Katz’s downfall, and it proves nearly as fatal to “Howard Katz.”

In productions both successful (“Doubt,” “Frozen”) and less so (“A Naked Girl on the Appian Way,” “The Paris Letter”), Mr. Hughes has proved skilled at letting his work breathe and allowing performances large and small to achieve their realizations at their own pace. But “Howard Katz” chugs forward like a fast-talking salesman with something to hide. This approach may play to Mr. Molina’s propulsive strengths — and make his occasional flashes of helplessness all the more affecting — but it also strands Mr. Hughes’s ludicrously talented supporting cast.

Only Jessica Hecht (as Howard’s beleaguered wife) and Alvin Epstein (as his conflicted father) find even the occasional emotional foothold. Mr. Epstein, Ms. Hecht, and Mr. Morton have all carried major productions recently, and yet here they are, trying to carve out a memorable line here, a meaningful stare there. And Elizabeth Franz, Christopher Durang’s original Sister Mary Ignatius and (in the 1999 Broadway revival) a near-definitive Linda Loman, gets three unexceptional scenes as Howard’s concerned mother and a cameo as a blue-hair at the local casino.

Casting has occasionally been an Achilles’ heel for the Roundabout, but casting agent Mele Nagler certainly earned her pay this time out (without throwing any phones, one hopes). The cast has a solid adversary in the redoubtable form of Howard Katz. Now all it needs is the ammunition to do battle.

Until May 6 (111 W. 46th St., between Sixth and Seventh avenues, 212-719-1300).