Sigurdsson, 22, arrived in south Wales on loan until the end of the season from Bundesliga side Hoffenheim in January and has gone on to score seven goals in 15 appearances, including a brilliant left-footed curler in the win over QPR on Saturday, to boost Swansea's bid to keep themselves in the top flight for at least one more season.
And Sinclair was full of praise for the midfielder, saying: "He has made a massive impact. He has come in, gone into that little hole behind the striker and he is scoring goals and setting them up. He has been a great addition to the side and hopefully we can keep him for next season, but we will wait and see how it goes. He has been quality."
Manager Brendan Rodgers is keen to put a deal in place to keep Sigurdsson at Swansea, with his goalscoring threat from the middle of the park having added a new dimension to his side.
But the chances of him doing so have arguably not been helped by the player's eye-catching form.
Sigurdsson, who has said he would welcome a permanent move, has two years left on his current deal in Hoffenheim, and they are unlikely to part with him cheaply given his current vein of form.
Rodgers said: "As far as Gylfi is concerned, we will have to review it between now and the end of the season.
"The chairman knows my thoughts on which players I would like to keep here at the club and hopefully there can be some discussions between Swansea and Hoffenheim.
"He is a top young talent and even if he wasn't scoring goals there would still be clubs that fancied him.
"He has scored seven goals now and just look at the way he took this one. He is a great striker of the ball with either foot."
Source: PA
Source: PA