April 8 (Reuters) - Juergen Klopp's decision to introduce Brazilian substitutes Philippe Coutinho and Roberto Firmino at halftime proved a masterstroke as both scored in a "massive" 2-1 victory away at Stoke City on Saturday.
The German surprisingly left both on the bench in favour of youngsters Ben Woodburn and Trent Alexander-Arnold but with Liverpool trailing at halftime to a Jonathan Walters header he reverted to Plan B despite fitness worries over both.
Coutinho equalised with a low shot 20 minutes from time and less than three minutes later Firmino scored a superb lob to seal victory and boost Liverpool's chances of finishing in the Premier League's top four.
Klopp said Firmino was suffering from exhaustion after his recent long-haul trips to play for Brazil, while Coutinho had lost three kilos due to illness in the past week.
"At halftime it was a difficult decision to make because it was not clear that Roberto and Phil would be ready for 45 minutes," Klopp told a news conference.
"Phil lost three kilos in the last three days. For most of us that would be good news! But for Phil and a professional football player, it is not as good. He came to the hotel this morning and said 'I'm fine'.
"But we knew he would have a low energy level, full enough for 30 minutes."
Klopp's side remain third, five points behind Tottenham and two ahead of Manchester City, having played a game more.
And while Arsenal and United can potentially threaten their place in the top-four shake-up, points on the board at such a late stage of the season are a distinct advantage.
"Massive, it's absolutely massive," Klopp said of the victory. "That's how it feels. We have won a few games this year, but this was really special.
"Today you could feel it immediately in the dressing room. Immediate everybody was like, 'That's very important!' Of course, we have to prove it next week and then the next week and then the next week, that's how it is, but it feels outstandingly good in this moment." (Reporting by Martyn Herman; Editing by Toby Davis)