Everton manager Roberto Martinez has been impressed by how quickly summer signing Ramiro Funes Mori has adapted to English football.
The Argentinian arrived at Goodison Park just before the deadline closed for ?9.5million and was initially expected to provide back-up to the established central defensive pairing of Phil Jagielka and John Stones.
However, injury to Everton's captain has seen Funes Mori enjoy an extended run in the side and he has flourished alongside Stones, who became the senior partner despite being three years the 24-year-old South American's junior.
"We can't wait to have our captain back but it is great to see Ramiro enjoying his football, adapting his football to the British game," said Martinez.
"It has been a massive step forward in his career but that is why we made a huge investment.
"To have John Stones at the level he is showing and the responsibility he has shown for 21 is incredible.
"When you have a new centre-half appearing in a new league you need guidance and John has helped him and they have developed a strong partnership."
Monday's visit of Crystal Palace presents a significant test, especially as their last two trips to Goodison Park have ended in 3-2 victories.
Martinez knows his side will have to be at their best.
"Crystal Palace are always a very difficult team to play against," he added.
"They have pace and power and the most significant aspect is they have been together for a long time and in modern football you cannot underestimate that.
"When you have a group of players who know each other and know how to be competitive that is really effective on the pitch.
"They have finished top-11 in the last two campaigns. They have a real good mentality and are capable of getting victories at Stamford Bridge and Anfield and that shows they are a mentally strong team.
"They have some individuals who can come up with an action which is difficult to stop and the dynamic is very athletic and they are very competitive.
"Obviously it is going to be a difficult game, as has been proven by their last two visits to Goodison Park.
"We will have to be at our very best but we have our own ambition and that is to get over the disappointment against Bournemouth (the last-gasp 3-3 draw) - it is important to get those points back with a good performance at Goodison."