Just call him as a witness and not say he is the whistleblower.
The reality is...he is a leaker....and a lying leaker at that. And this is the same pattern as Comey's little leak.
Testimony from the whistleblower is probably not needed. It is like a neighbor calls the police and says, “I hear screaming and yelling in an upstairs apartment.” The police come and find a woman bruised and bleeding, a man with skinned and swollen knuckles, and furniture in disarray. They do NOT need the neighbor. The true situation is right before their eyes, and the neighbor is not a witness as to who did what to whom.