West Ham boss Slaven Bilic paid tribute to Sam Allardyce ahead of the Sunderland manager's return to his former club in the Premier League on Saturday.
The match at Upton Park sees Allardyce, who managed the Hammers for four seasons between 2011 and 2015, face his successor for the first time.
Bilic, who at 38 per cent has the best win rate of any Hammers boss in the Premier League era, congratulated his counterpart on his accomplishments ahead of the clash and talked up Sunderland's chances of avoiding relegation.
"Sam did great for West Ham," said the former Croatia boss.
"He has managed for 20 years very successfully and he took over West Ham at a moment when we were in the Championship. He got us up straight away and stabilised us in the Premier League, so he did a great job here.
"Sunderland are very organised, they are showing not only the quality, but the character. They have a quality not only on breaks, but also in different ways.
"There is still a long way to go for them, but they have a big chance to stay in the league."
West Ham impressively moved into the FA Cup quarter-finals with wins over Liverpool and Blackburn Rovers this month, but could do with a victory over Allardyce as, in the league, they have won only one in five and slipped down to seventh in the table.
Despite their league dip, though, the Hammers are flying at Upton Park having not suffered defeat there in the top flight since August, while Sunderland have struggled on their travels, winning just two of their last 15 away league games.
But the Black Cats have picked up four points from their last two matches against Liverpool and Manchester United to boost their survival hopes, with the gap to Norwich City in 17th now down to one point.
Sunderland striker Dame N'Doye, who experienced relegation while at Hull City, has been impressed by the determination within the squad over recent weeks.
"There is a good atmosphere in the dressing room and the lads are very focused," he said to the Sunderland Echo.
"They have a strong mentality that they will stay up, which is the most important thing. Every year, you work hard to stay in the Premier League. Nobody expects to go down, but someone has to.
"I didn't want to be relegated at Hull, but it happened. Now it is a new challenge and I have to forget about that and concentrate to stay up."
Bilic has Andy Carroll (groin) and Cheikhou Kouyate - who had his red card against Blackburn rescinded - available, while Winston Reid (hamstring) and Diafra Sakho (thigh) are closing in on returns but remain doubtful.
Sunderland have been boosted by recent injury absentees Younes Kaboul (foot), Jan Kirchhoff (hamstring) and Sebastian Larsson (knee) participating in full training this week, but Jeremain Lens (hernia) is still expected to be missing.
The two teams drew 2-2 at the Stadium of Light in October in what was Dick Advocaat's last game in charge of Sunderland prior to Allardyce's arrival.
Key Opta Stats:
- West Ham have won seven and lost just one of the last 10 Premier League home games against Sunderland.
- West Ham have conceded the highest proportion of goals in the first half of matches this season (61 per cent).
- Dimitri Payet has scored or assisted 12 Premier League goals this season (seven goals, five assists); twice as many as any other West Ham player.
- If West Ham win this match, it will be their highest-ever haul of points after 27 Premier League games beating the 42 they had earned in 2005-06.
- Sunderland have allowed their opponents 158 shots on target against them this season, more than any other team in the top flight.
- Sunderland have conceded the joint-most penalties in the Premier League this season along with Norwich City (7).