Does an employee have a case of tortious interference, defamation or slander?

In this situation, an employer had a layoff of union and non-union employees. A company officer stated that one of the non-union, at-will employees he laid off "would never work at the company again." This information was diseminated throughout the organization.
For several years prior to the layoff, allegations of embezzlement were made against this employee by union members / officials, both on and off company property. Demands for the removal of this employee were made by the union personnel in contract negotiations, grievence hearings, company meetings and private meetings with the company officer. The charges were false.
The company officer also requested the employee be party to illegal acts in order to resolve a business issue. The employee refused to carry out the actions and instead offered legal options for resolution of the business issue. The legal alternatives were dismissed by the officer.
This appears to be Tortious Interference in Employment by both the company officer and the union.
This person believes their reputation and career have been harmed. It also appears the person may have a case for defamation and slander.
The company placed a temp in the vacant position shortly after the layoff and is poised to fill the position with a new hire.
The laid-off employee is considering legal action. Does this case appear to be strong enough to persue?