What is the test for determining whether counsel was negligent in pursuing a claim for medical malpractice?

"(1) [T]he nature of the mistake or neglect; and (2) whether counsel was otherwise diligent in investigating and pursuing the claim. [Citations.] In examining the mistake or neglect, the court inquires whether 'a reasonably prudent person under the same or similar circumstances' might have made the same error. [Citations.] In addition, '[u]nless inexcusable neglect is clear, the policy favoring trial on the merits prevails.' [Citation.]" (Bettencourt v. Los Rios Community College Dist., supra, 42 Cal.3d at p. 276, 228 Cal.Rptr. 190, 721 P.2d 71.)