The Stars blew the chance to finish in top spot and secure two home finals when they crashed to a six-wicket loss to the Perth Scorchers on Saturday night.
Perth skittled the Stars for 130 in 18.2 overs before chasing down the victory target with 19 balls to spare in front of 48,608 fans at Optus Stadium.
The Scorchers (7-3) snared top spot for a competition-record sixth time, while the Stars (6-4) will finish either third or fourth, depending on the result of Sunday's clash between the Sydney Sixers and Brisbane Heat at the Gabba.
The Stars are the only team in the BBL yet to win a title - and they'll have to win three-straight finals - at least two of them away from home - to snare the crown this season.
One of their biggest concerns is the form of Maxwell, who was joint player of the tournament last season but has scored just 67 runs across seven knocks this campaign.
Apart from an unbeaten 39 against the Thunder and a 20no against the Renegades, Maxwell has posted scores of 2, 1, 1, 1 and 3.
Maxwell was relegated to No.7 in the order against the Scorchers on Saturday night.
The 37-year-old entered the fray at 5-100 in the 14th over but he made just three off eight balls before skying a catch to the boundary.
Siddle, who at 41 still remains a key part of the Stars' pace attack, says Maxwell has proved time and again he can fire when his back is against the wall.
"He's in that position at the moment," Siddle said of Maxwell, known as The Big Show for his ability to post blazing knocks in big moments.
"You've just got to let him go, just to make sure he's comfortable and happy.
"He's starred at World Cups in knockout games and starred in knockout tournaments.
"He'll know what to do, so I think we'll definitely see the best of him next week."
Maxwell is also renowned for his excellent fielding, but he dropped a catch he would normally take late in the Scorchers' innings.
Siddle praised the way Maxwell has been able to impart his knowledge on the group despite his lack of runs.
"He would have loved to have done more, but he's still been great," Siddle said.
"The way he talks to the boys and especially the young batsmen, he's helped them, and they probably had better seasons than we expected anyway.
"So as much as he mightn't have starred with the bat, his words and his leadership with those younger batsmen has he played a great role."
