Brett Hodgson’s hosts scored either side of half-time through Adam Swift and Jake Connor but the visitors were not to be denied and ran out worthy victors.
Yet the loss of McShane during the opening quarter left Powell facing a nervous wait ahead of Monday’s home clash with Wigan, which he looks certain to miss.
Powell said: “We’re not exactly sure of the injury but it’s in that area of abdominal/groin, so they are sort of all interconnected together.
“We will get an idea when he’s had a scan, but Paul McShane doesn’t come off unless he’s injured.
“I expect it could be a decent injury and he will miss the Wigan game on Monday, but Adam Milner was class when he came on.”
Turner struck twice during the first half either side of a well-taken effort from Swift and continues to prove an astute acquisition.
The 32-year-old centre or winger was signed from Huddersfield at the end of last season and helped Castleford to reach last month’s Challenge Cup final, where they lost to his former club St Helens.
Powell added: “Jordan is coming up with big plays and I think he’s playing some of the best rugby of his career.
“It was a tough game which ebbed and flowed and I thought we showed great courage and resilience.
“We were so tough tonight and the boys are handling these short turnarounds really well.
“After losing the Challenge Cup final at Wembley, the boys agreed we could knuckle down and have a real go at making the play-offs. There is a long way to go, but we have a chance.”
Second-half tries from Richardson and Evalds sealed the win while Connor touched down in the second period for the hosts, who saw centre Carlos Tuimavave forced off with a recurrence of an Achilles injury.
Hull boss Hodgson said: “Carlos has had an ongoing Achilles problem which flared up again, so we had to replace him.
“I was really disappointed with the fact that we couldn’t get ourselves up for this game.
“Our players are hurting and we need to take that hurt and prove that we can win the energy battle when we play Salford on Monday.
“If we’re good enough over these next four games, we will make the play-offs.”