The Swansea-based region confirmed last week that they will release the British & Irish Lion at the end of the season.
Phillips has barely featured for the reigning Magners League champions in recent weeks and was omitted from the match-day squad to face the Newport Gwent Dragons last weekend.
The Ospreys took the decision in a bid to protect the scrum-half from the red-hot derby atmosphere at Rodney Parade.
But Humphreys insists Phillips is in contention for the must-win clash against Munster on Saturday and is confident that he will fire on all cylinders if selected.
"Mike's available for selection. He was last week and is this week.
"He's been extremely professional and has done everything asked of him. He's trained hard and his reaction has been positive.
"Mike's a competitive person and player, as soon as you cross that line you forget what's happening off the field. You want to do well for yourself and your team-mates.
"He's been extremely professional and hopefully he'll be the same until the end of the season."
While Munster have already secured a home play-off semi-final, the Ospreys' shock defeat to the Dragons put a major dent in their own play-off hopes.
The reigning champions dropped to fourth in the league but the Cardiff Blues are breathing down their necks two points behind and with a game in hand.
And Humphreys is adamant the Ospreys must win their two remaining games to have any chance of staying in the play-off places, starting with the red army.
"We're definitely in a must-win situation. Anything other than a win puts us out of it. The stark reality is we are reliant on other people's results now.
"Munster are a proud bunch and if we were in their position we'd like to keep the momentum going. I don't think they'll be taking their foot off the throttle for us at all.
"I expect them to turn up fully loaded on Saturday.
"It's the place where we beat them in the Heineken Cup, we played well that day, and I'm sure they'll want to put that right."
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