Murphy must have his reasons. There are some urgent things he can't say outright, but his hints were already very clear.
Calling under the guise of asking about Number Thirteen, yet having no idea what Number Thirteen is actually doing, Murphy clearly didn't call Gao Yang because of Number Thirteen, though Murphy did learn about Number Thirteen's issue through the process.
If Murphy didn't call because of Number Thirteen, then connecting it to his comments about safety, enemies, and so on, it's easy to conclude that Murphy made this call just to issue a warning. When linking it to what he said about elite forces, it's obvious the people coming are formidable players—and there's quite a number of them.
The last time Gao Yang chatted and drank coffee with Murphy, it was in preparation for taking out Tomler. Murphy mentioning this now is very deliberate—he's telling Gao Yang that people under Tomler are preparing to move against him, and besides Krulney, there can't be anyone else.
