Swansea are thought to want to sign two or three more players, with Hull's Sam Clucas a major transfer target.
Last season's top scorer Llorente is not yet fit and sat out Saturday's 4-0 home loss to Manchester United.
"If we can service Fernando up front with crosses, he is a different type of player for us," Fernandez said.
"If he's ready and he can join us he can help... we need to score to take points, to win games."
Swansea have failed to find the net in the Premier League so far this season, after beginning their campaign with a 0-0 draw at Southampton.
Llorente, who scored 15 goals last season, could play some part in the trip to Crystal Palace on Saturday, 26 August, having broken his arm during a family holiday in the summer.
Midfielder Ki Sung-yueng is also sidelined after having knee surgery in July and is expected to be out for at least another two months.
But following fellow midfielder Sigurdsson's £45m sale to Everton, Swansea have the funds to strengthen before the transfer window closes.
"We need to work hard and hope players come in or recover from injury and can help to make a better squad," added Fernandez, who captained Swansea against United.
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"We expect two or three new players to come in. We need to better, to create more chances, to play more football. We need to work in the training ground.
"Of course Gylfi is a great player, who last season scored nine goals and 13 assists - those are high numbers - so we need to find a player in that position who can do the same."
Swansea had hit United's crossbar early and with 10 minutes remaining only trailed to Eric Bailly's 45th-minute opener.
But as the Welsh side went in search of an equaliser they conceded three goals in just three minutes and 41 seconds, as the visitors exploited the space to devastating effect.
"I think the result was harsh on us," Fernandez added.
"They were very good on the counter-attack and took advantage of our changes in the second half.
"There are no excuses for us, we need to continue to work hard. But I think we played well in large parts and we should take positives from that."
Before next weekend's trip to Selhurst Park, Swansea go to MK Dons on Tuesday night in the EFL Cup second round.
Federico Fernandez says Swansea need to replace midfielder Gylfi Sigurdsson but believes the return of striker Fernando Llorente to fitness is also crucial.