The 34-year-old from Pontefract has played over 300 games for the Tigers in two spells with the club and made his professional debut for the West Yorkshire side in 2004.
He signed a two-year extension at the beginning of 2019, with that contract set to expire at the end of the season.
Castleford open their Super League campaign against Warrington Wolves on Sunday and Shenton’s focus is on making 2021 a “special year” for the Tigers.
“I have put it to the back of my mind at the moment,” he said of his contract situation.
“It is just all about enjoying it and making sure it is a special year. There is no official decision yet.”
Head coach Daryl Powell confirmed last week that this season would be his last at the club. He first joined the club in 2013, the same year that Shenton made his return to Wheldon Road after a three-year spell at St Helens.
Shenton admits it is hard to imagine the club without Powell at the helm and wants to make this campaign one to remember.
He added: “With what happened last year and the news about Daryl leaving, it feels this one will be a good one for Cas.
“We have had a really good pre-season, there is some real excitement around the boys and the new signings have slotted in well. Daryl and I have got a bit of a close relationship so I have known for a couple of weeks but I think some of the boys were shocked.
“It is hard to imagine him moving on, he has been here for a long time now. He has done one hell of a job for us.”
Shenton believes that Powell has “transformed” the Tigers during his time in charge, with the former Great Britain international the longest-serving head coach in the club’s history.
“He is a fantastic leader,” added Shenton.
“He has transformed us not just on the field but off the field as well. He leads the way in everything and sets the standards.”
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