Rangers have confirmed the signing of Dundee United striker Jon Daly.
St Mirren defenders Sean Kelly and Jason Naismith have signed new one-year contracts with the club.
Former Italy forward Alessandro Del Piero has announced he will activate the second year of his two-year deal to remain with Sydney FC.
Overseas clubs were reportedly lining up bids to tempt Del Piero away from the Harbour City, but the 38-year-old and his family wanted to extend their stay.
"I am very happy to be staying at Sydney FC for another season," Del Piero said.
"I chose Sydney FC at the beginning of this season because I wanted to show my love of football in another country and I have enjoyed the challenge and my time at Sydney FC and in Australia.
"I have always said I want to continue that for next season but first we must work hard for success on the field for the rest of this season."
Football Federation Australia chief executive David Gallop said Del Piero's decision to stay was a huge boost for Australian football and the A-League.
"If he'd gone just one season then people may have questioned how he felt about the A-League," Gallop said.
"This is very much him saying he had a great experience and he wants to have it again.
"That's great for football in Australia and the A-League and it's exciting to have him signing for a second season."
Del Piero has scored 11 goals this season to revive his team's finals hopes.
The decision to stay and activate the second year of his Aus dollars 2million-per-season deal was met with delight by Sydney FC Chairman Scott Barlow, who told the club's website: "I am delighted to announce that Alessandro Del Piero will continue to be a Sydney FC player for the 2013/14 season.
"Alessandro's arrival at Sydney FC has been a wonderful success for Sydney FC and the A-League both domestically and internationally.
"His performances on the field have been tremendous, highlighted by him becoming the leading goalscorer for Sydney FC in a single season, but off the field he has also delivered unprecedented interest and profile for Sydney FC across all levels of the club.
"We look forward to working together with Alessandro to increase the profile of Sydney FC and football in Australia as we strive for success on the pitch for the remainder of this season and next."