The West Yorkshire club host Saints tomorrow looking to become the first side to beat Justin Holbrook’s team in 2019.
St Helens have won all six games so far and are emerging as early candidates to finish as League Leaders’ Shield winners for a second year running.
However, they fell at the semi-final stage of both competitions last time with Castleford – who finished top but beaten Grand Finalists in 2017 – also coming home empty-handed when it comes to silverware.
Third-placed Tigers have lost only once this term and Powell said: “The boys are in good spirits and we’re looking forward to it.
“I don’t think we’re at our best yet but you don’t need to be at this time of year.
“The two most consistent teams over the last three years of Super League in the regular rounds are us and Saints.
“The challenge for both teams is to win the big games; that’s something you can point at Saints last year and at us a little bit last year and in 2017.”
Meanwhile, 33-year-old former Kiwi utility back Ben Roberts, who played 78 games in just over four years at Tigers but was dogged by injuries, has been released by ‘mutual agreement’.
Powell said: “It’s fair to say it’s been frustrating for both Benny and ourselves he hasn’t been able to get on the field as often as he’d like and unfortunately that looked increasingly unlikely.
“He’s had some fantastic times and really was pivotal to us being outstanding in 2017. In amongst that, he’s found it really difficult physically to get onto the field and given his standing within the squad it’s also become difficult for us from that perspective.”