Marin Cilic believes he has enough energy left to seal a Davis Cup triumph for Croatia against Argentina.
Cilic and Ivan Dodig gave the hosts in Zagreb a 2-1 lead with a 7-6 (7-2) 7-6 (7-4) 6-3 win over Juan Martin del Potro and Leonardo Mayer in the doubles on Saturday.
Now, Croatia are just a win away from their second Davis Cup crown and first since 2005.
Cilic can complete the job with a win over Del Potro, who holds an 8-2 head-to-head record against him, in the fourth rubber.
"The atmosphere was absolutely fantastic as our fans carried us throughout the contest," Cilic said.
"Del Potro is an incredibly good player but I am confident I have enough left in the tank to finish the job."
Del Potro remains optimistic about Argentina's chances despite his nation needing two wins on Sunday.
The world number 38 said: "I know him [Cilic] very well because we grew up together playing at all sorts of tournaments.
"He has done exceptionally well this year and will be backed by a passionate home crowd, but as ever I will do my best to prevail and give us a fighting chance of winning the Davis Cup."
Ivo Karlovic and Federico Delbonis are scheduled to meet in the fifth rubber.