"Questions of judgment" or "strategies at trial" are frowned upon as legal malpractice departures.  A strong body of law holds that trial is an art and not a science, and choices of strategy, even though eventually losers, will not be the means to a successful legal malpractice case.  Selection of witnesses, of experts, and of the questions to ask at trial (just to name a few) are unsuccessful claims.

In O’Callaghan v Brunelle ; 2011 NY Slip Op 04095 ; Decided on May 17, 2011 ; Appellate Division, First Department found that  the "allegations that defendants’ failure to call the witness, who consented to the NYSE’s Hearing Panel’s finding that he engaged in conduct constituting improper trading arrangements and violated various rules, constituted legal malpractice "  were insufficient, and in fact, refuted by the documentary evidence.
 

Put more simply, a failure to call a witness will rarely support a legal malpractice case.  In a different setting the failure to call an alibi witness might be ineffective assistance of counsel, but the standards, and the way the AD looks at these situations is just a polar opposite.