Andy Murray had to dig deep to ensure Great Britain made a winning start in their Davis Cup round-robin tie against Switzerland in Manchester.
With Britain aiming for a place in November's eight-team knockout stage, Murray edged past Swiss debutant Leandro Riedi 6-7 (7-9) 6-4 6-4.
Cameron Norrie can seal victory by beating Stan Wawrinka later on Friday.
If Norrie loses, Dan Evans and Neal Skupski can secure a second straight GB win by taking the deciding doubles.
Even if Britain beat the Swiss in the best-of-three tie, they cannot secure qualification until Sunday's final tie against France.