The debate over who should be the world champions' number one has been reawakened by Real Madrid coach Carlo Ancelotti's decision to once again keep Iker Casillas on the bench in favour of Diego Lopez.
Despite his lack of match practice, Casillas was still preferred by Del Bosque for the Confederations Cup, however Victor Valdes' sensational early season form for Barcelona means he is the favourite to start in Helsinki.
"We have decided already who will be the goalkeeper but we will communicate that tomorrow," Del Bosque told a news conference on Thursday.
Valdes was given a ringing endorsement from club team-mate Xavi Hernandez, who praised his patience at waiting for his opportunity at international level.
"I am not objective when speaking about him because we have a friendship off the field but he is an example on the field and as a team-mate.
"He has waited patiently for his opportunity to come to the national team and play, I don't know if he will do so against Finland but his behaviour throughout his time in the national team has been exemplary."
Del Bosque also has a selection headache in central defence and midfield due to injuries and suspensions.
Gerard Pique is banned following his red card in the final of the Confederations Cup against Brazil and Inigo Martinez's withdrawal due to injury earlier in the week means that Raul Albiol will almost certainly partner Sergio Ramos at the heart of the defence.
The usual midfield pair of Sergio Busquets and Xabi Alonso are also missing through injury so Bayern Munich's Javi Martinez is likely to start alongside Andres Iniesta and Xavi in midfield.
"There are injuries that we need to play down because we have people behind that will do well," said Del Bosque.
"Obviously, they are important absences. The spine of our team has been based around Busquets and Alonso who are not there but in Spain there are many midfielders in this position and for sure one of them will solve this problem."
Spain need to win all three of their remaining qualifiers to guarantee their place in Brazil next year as group winners.
However, the one major blip in their qualifying campaign so far came against the Finns back in March when Teemu Pukki's late equaliser secured a point for the unfancied Scandinavians and Del Bosque is expecting a similar game on Friday.
"We have just now been revising the game in Gijon, they defended deep a lot but then had very quick transitions.
"We expect a similar game to the one in Gijon, we need to have patience but also energy to compete with a team that is going to make things very difficult for us.
"I think we need to win the three games that we have left. All the opponents can make things difficult for you, we have already had difficulties with Finland and Georgia."