Wigan players were incensed at the time and there were boos from the home crowd as video replays flashed up on the big screen at DW Stadium.
Sene-Lefao, 29, seemed to hold his arms out in apology as he left the field, too, but some views of the incident appeared to back up Powell’s claim.
Asked if he expected the former Cronulla Sharks star to get a lengthy ban, the coach said he had “no idea”.
But Powell added: “Knowing what he’s like, there’s no intent in there.
"I’m not sure he intended to do it and I’m not sure he made contact; I thought his knee hit the floor.
“Jesse is a Godly man. He prays every minute he can. There’s not an awful lot of malice in him.
“I’ve never seen any malice in him at all so I don’t think there’s a massive amount of intent there.
“It’ll be interesting.”
That said, Powell accepted his side had been out-played by Wigan who secured second spot with an impressive seventh successive win and have now won 12 of their last 13 games.
Granted, Castleford were only 4-2 down at the break but two tries early in the second half from Zak Hardaker and Oliver Gildart left them chasing and they were 18-2 behind by the point of Sene-Lefao’s indiscretion.
Tigers - who were flat and aimless in attack - remain in fifth spot but Hull FC will replace them in that final play-offs place if they avoid defeat against leaders St Helens at KCOM Stadium this evening.
Half-back Jake Trueman, 20, scored a hat-trick last week as Castleford beat Hull to replace them in fifth.
But just six days later, the young Great Britain hopeful found life far more difficult against the steely reigning champions and now they face an anxious wait to see if they qualify.
Trueman’s kicking game was badly off, twice rolling kicks dead to concede seven-tackle sets, and, despite a raft of good ball in both halves, he and the rest of his side failed to create anything of note.
Their only try came via Cheyse Blair after the final hooter.
Powell conceded: “I just don’t think we were smart enough.
“Truey had an unbelievable game last week. Maybe he got too many pats on the back.
“I don’t think he handled this week well and I don’t think Jamie (Ellis) did; our half-backs didn’t play well tonight.
“Our kicking game was poor and we looked disorganised for too much of the game.
“Clearly we are going to have to be better than that - and we do have potential to be a whole lot better than that.
“Hopefully we can get another opportunity. It’s a big game for Hull tomorrow and we’ll see what happens.”
He described the loss as “disappointing” and added: “We wanted to come and win and our attitude was great for the most part.
“But we just got rumbled at the start of the second half.
“It was an absolute disaster for us at the start of the second half not catching the kick-off and then conceding two quick tries.
“The game was won and lost there.
“Our attacking game was poor all night; it was just blunt.
“But Wigan defended well. They have a great defensive team that comes after you.
“We’re not good enough in these games at the moment where teams are defending really well at us.”