The Tigers were sixth in the betting at 11-1 with league sponsors Betfred to win the Grand Final at the start of the year while Salford, who survived in the top flight by the skin of their teeth last October, were 66-1 outsiders.
Now Daryl Powell's table-toppers are the 7-4 favourites while the third-placed Red Devils are a 20-1 shot to lift the trophy for the first time at Old Trafford on October 7.
Castleford are setting a hot pace, having scored more points and conceded fewer than any of their rivals, and winger Greg Minikin says coach Powell will ensure there is no complacency as they look to complete the job.
"I think we can keep it going if we stay grounded and Powelly has done a lot of work to make sure we don't get ahead of ourselves," said Minikin, who is second behind team-mate Greg Eden in the Super League scoring chart with 13 tries.
"There is a confidence there but it is a controlled confidence, we're definitely not getting ahead of ourselves."
The Tigers' next fixture is a derby with Leeds Rhinos which will bring down the curtain on the 11th Dacia Magic Weekend at St James' Park, Newcastle, on Sunday.
Ian Watson's Salford also play on Sunday, against local rivals Leigh Centurions who will make their first Magic Weekend appearance.
Salford are one of just three teams to have beaten Castleford this season and proved it was no fluke by winning six of their seven matches since to close to within two points of the leaders.
Former Wigan Warriors and England prop Lee Mossop, who is in his first season with the Red Devils, insists their success has come as no surprise to the players.
"We knew that, if we played to our potential, we could have a season like this," Mossop said.
"Having said that, we're only halfway and there's a lot more games to be played. We're real conscious that it only takes two or three results to go the other way and you're right back down to that fight.
"Watto has got us real focused. We're taking each game as a sort of cup final and it starts again this week. Leigh are on the back of seven losses so they're desperate for that win.
"But I'd like to think we can keep it going. We're not going to change anything, we'll keep doing what's got us in this position which is work hard. We're not a team full of superstars, we have to graft for every win we've got this year and we'll keep doing that."
Mossop believes most of the credit for Salford's resurgence should go to boss Watson, who has emerged from the shadow of Tim Sheens to prove his credentials as one of the brightest young British coaches in the game.
"From my point of view, being around successful teams, as long as the coach is honest with his players, they will respect him no matter what," Mossop said.
"All the players want to play for him and at the same time we've got competition for places.
"In my position we've got five or six front rowers all going for four places in the team, so it's real good at the minute. We push each other hard in training and it breeds that competitiveness.
"I was used to that at Wigan. I know from experience it's exactly what you need to be at your best.
"If you relax or start taking your place for granted, that's when your performances start dipping."