The 26-year-old Pontypridd fly-half made his regional debut against Worcester Warriors in the LV=Cup last weekend and is poised to have another chance against the Ospreys on Friday.
Rhys Patchell has been ruled out of the clash with a shoulder injury, while Gareth Davies is rated 50-50 after suffering a groin strain.
That leaves semi-professional Humberstone as the only fit fly-half candidate training with the Blues and Baber reckons the former UWIC star is playing for a full-time future.
“Rhys has a bit of a problem with his shoulder and Gareth picked up a slight strain last week,” said Baber.
“Gareth is only a slight strain it’s just a question of whether he will win the fitness race for this weekend. It’s not as bad as first thought – there has been better news over the last few days.
“But we have Simon Humberstone who performed well and has impressed us enormously since he has come in – a lad who has being playing in Pontypridd but taken a step up here.
“He is quite capable of holding a position here and it’s up to him. He’s been given an opportunity and he needs to put in performances.
“When you’re a young fella and are given an opportunity like this you have to get in and take it. This could be the opportunity he has been waiting for. He has an opportunity to get a contract.”
And Baber expects a full-blooded Welsh derby at the Liberty Stadium, despite the lack of stars due to international duty.
“It’s a local derby; it will be physical and are planning around how they play the game,” said Baber.
“There will be energy, edge, two teams that know each other well and a lot of competition between the group. A lot of the boys would have played each other through the age-grades and they know each other well. We’re hoping for a good crack at them on the weekend.”
