The Age has since learned that Franklin complained of tightness in his hamstring in the club’s first session back last Monday.
The Swans wouldn’t comment on whether he had a scan last week, but confirmed that he missed the team’s main training session last Wednesday.
He then completed only light running sessions last Friday and Monday this week, before building up on Wednesday when he injured himself.
Sydney confirmed that Franklin would have scans on Thursday.
Swans football boss Charlie Gardiner said the club wouldn’t know the extent of the injury until it received the results of scans.
“Lance hadn’t been participating in contact training this week as we have been gradually building his training load,” Gardiner added in a statement.
“He was doing some routine running drills at Lakeside Oval this morning when he experienced pain in his hamstring, which is clearly a concern.
“We won’t know the extent of the injury until we have the results of the scan, but it’s a disappointing setback for Lance as he had been progressing well in his preparation for round two.”
Franklin has a history of hamstring injuries.
His 300th game was put on hold after he injured a hamstring in a win over Hawthorn last June, where he was stuck on the bench for nearly 10 minutes while trying to come back on.
It was his second hamstring injury of the year. That was in round 14 and he didn’t play again until round 23.
The news follows an injury to Sam Reid earlier in the week.
Reid injured a calf at training on Monday and is set to miss Sydney’s round-two match against Essendon at the SCG.
Franklin has only played one game since the second half of last year and his pre-season was further hindered when he went under the knife in January for his troublesome knee.
He was pictured recently training strongly while in isolation and the club had described the extended break as a “silver lining” for the 33-year-old.
Franklin is into his seventh year of a nine-year contract at Sydney after leaving Hawthorn.
Sydney aggressively pursued Essendon’s Joe Daniher during last year’s trade period, with the club identifying him as Franklin’s long-term successor as the Swans’ power forward.
Sam McClure is a sport reporter for The Age and winner of ‘best news reporter’ at the AFL Media Association awards.