The versatile Northern Ireland international is one of the longest-serving players at Elland Road, joining from Brentford in 2015, but as the team has upped its levels in that time, so has he.
Dallas was a league ever-present in an arduous season, scoring eight goals, but it was the quality as much of the quantity of the football he played, picking up the club's player's player of the year and the overall player of the year prize.
The 30-year-old appeared to have been earmarked as the first-choice left-back at the start of 2020-21, his main job in the promotion campaign that preceded but became indispensable as a central midfielder.
Dallas started full-back or wing-back in 15 of the first 18 matches of the season, but only five of the final 18.
Dallas joined the club as a winger but when Marcelo Bielsa arrived as coach in 2018, the need for players with the intelligence and versatility to change position as the team's formation alters in a game became crucial. It is usual a change of rle for Dallas which is fundamental to a shift, as Leeds move from a back four to a back three or some other alteration in response to the pattern of the game and the approach of the opposition.
In April Bielsa paid Dallas the huge compliment of comparing him to Javier Zanetti, the Inter Milan legend who won 143 caps with Argentina, many of them when compatriot Bielsa was coach.
“I had a player like Dallas, Javier Zanetti, and also Julio Saldana, who I had when I first managed at Newell’s,” said the Leeds coach.
“Those two players are very like Dallas in terms of their versatility.
“Dallas is a very potent, powerful player. He can play with either foot, his right or his left, he’s good defending.
“He has the capacity to combine as well as make runs, which allows him to flourish playing in the middle.
“He has a change of rhythm and surprise when he attacks. It’s very difficult to find all that in just one player.”
For such a reliable player, Dallas has really hit the heights at times too.
His performance at Manchester City in April, where he continued to make positive runs from central midfield despite Liam Cooper being sent off in the first half, was exceptional and rewarded with both Leeds's goals, and his matchwinner was voted the club's goal of the season.
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