Wales international Steve Morison grabbed his 13th goal of the season in Millwall’s 2-0 home win over Barnsley, yet again highlighting his credentials to the Premier League.
But a new two-and-a-half-year deal is on the table and Jackett said: "We've talked to Steve. I don't know at what stage those guys are at but we are in negotiations.
"It was a good finish, he kept it down well on his left foot outside the post. It was an easy one to miss on your wrong foot and it was the vital first goal."
A fourth straight home win has moved his side up to eighth, just three points shy of the top six.
"It was a very good start and a good win after the defeat at Leicester last week," he added.
"The second half was a bit surreal but we saw it through.
"We don't want to get too far ahead of ourselves. It's the old adage of taking each game as it comes, and if we are still up there in March then we can start looking in the right direction. You have to look short term in this industry."
"It took us two goals to get going," said Tykes manager Mark Robins.
"We were lacklustre. You know when you come to The Den about Millwall's energy and that they work hard, but we didn't get to grips with it.
"We were a soft touch, which was disappointed. But it was our third game in six days and it's taken its toll."