The Ecuadorian winger has not played for Swansea since the FA Cup defeat to Oxford United in January.
Despite featuring in Ecuador's World Cup 2018 qualifiers with Paraguay and Colombia during the international break, Montero has not appeared for the Swans since the shock 3-2 FA Cup third-round defeat to Oxford United in January.
The 26-year-old, who signed for an undisclosed fee from Morelia in July 2014, started the season in good form, earning praise for sparkling performances against Chelsea and Newcastle United.
However, the last few weeks have seen the winger fall behind Modou Barrow in the pecking order, with the Italian demanding that Montero show improvement in order to force his way back into the team.
According to WalesOnline, Guidolin said: “Montero has to improve his play with other players, for example when we haven’t got the ball.
“He isn’t ready in my opinion – but his qualities are important.
The 60-year-old suggested Montero would now have work even harder than before, with Barrow continuing to impress as Swansea look to secure Premier League safety.
“Week by week, I hope to have the possibility to see him. Modou is improving. I hope Jeff will do the same," Guidolin continued.
“As a manager I have seen some qualities and characteristics which are important, but he also has to improve.”
Swansea travel to Stoke City on Saturday, knowing a win will leave them with a very strong chance of preserving their Premier League status.