Battle is a free agent at season's end and has been heavily targeted by Hawthorn.
Half-back Sinclair, who last year re-signed until the end of 2027, wasn't planning on getting in his teammate's ear before arguably the biggest decision of his career.
"It's hard. You don't really know the ins and outs to be honest," Sinclair told AAP.
"I'd love him to stay, but he's got a lot to weigh up, no doubt, and I'm sure he'll do what's best for him and his family.
"Hope he stays, he's had a great year, great couple of years, really integral part of our back line and really reliable player.
"I love what he brings and hopefully he'll be in Saints colours next year, but it's hard to influence too much. You don't want to step in and feel like you're probably unwelcome.
"But at the end of the day, it's his decision, and yeah, we'll live with it either way."
St Kilda's defenders are gearing up for trying to restrict Geelong spearhead Jeremy Cameron at Marvel Stadium on Saturday night.
"Between Wilks (Callum Wilkie), Josh Battle can play a bit higher, Mase (Wood) on the wing is a bit of a taller type as well, hopefully we can get it sorted," Sinclair said.
"He's certainly caused us some trouble over the past couple of years, but they've got a number of incredible players."
St Kilda (14th, 9-12) won't play finals but are determined to finish strongly against Geelong, then Carlton, to set themselves up for next year.
"We're just trying to set ourselves up for the future, for future success. So for us, that's about giving everything for every game," 29-year-old Sinclair said.
"We don't just want to get to the line and have a poor finish to the year, because it can really derail you going into your break.
"We want to give the fans something to be proud of these last couple of weeks, and really just keep building for what's next, whether it's next year, year after that, who knows? You never know what's around the corner in footy.
"We've been challenged so much this year, but I just love the way the group's responded.
"Individually players have really shown heaps to dig in and respond, get back to their best footy.
"I really believe in what we're building with the coaches and the players, and it keeps me excited heading into my 11th year next year, just a bit of a breath of fresh air."
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