Jagiellonia Bialystok Sandomierski's career began at
Jagiellonia Białystok, starting in the reserve side from 2006. He played in four games and then was loaned out to
Lech Poznań. He made two appearances in the fourth division, after which he returned to Jagiellonia. In the 2007–08 season, due to an injury to Jacek Banaszyński, Sandomierski made his
Ekstraklasa debut against
Cracovia in which he conceded two goals. By the end of the competition, he appeared in four other matches. Sandomierski then sustained a serious injury which excluded him from play for half a year. In January 2009, he was loaned to
Ruch Wysokie Mazowieckie, where he played as a first choice goalkeeper. Prior to the 2009–10 season, he returned to Białystok. Sandomierski got his chance for Jagiellonia after
Rafał Gikiewicz suffered a poor run of form. During his time at Jagiellonia, for six matches in a row, Sandomierski kept a clean sheet. His streak lasted 564 minutes, a club record, and ended in a clash with
Ruch Chorzów.
Blackburn Rovers On 31 August 2012, Sandomierski signed on a season long loan with
Blackburn Rovers with a view to signing long-term. He made his debut for
Rovers against
Cardiff City in a 3–0 defeat conceding two goals one of which was a penalty, coming on for injured counterpart
Jake Kean in the 52nd minute. Sandomierski's second appearance came against
Sheffield Wednesday after it was announced that Kean would miss the remainder of the season through injury. Caretaker manager Gary Bowyer expressed his faith in the
Polish international, however Rovers were beaten 3–2 on the day. His next match saw him gain two impressive clean sheets against Derby County and Huddersfield Town. He then conceded four goals against Watford in a not so impressive match. In his next match against Millwall he only conceded one goal but had a fairly comfortable game. == Coaching career ==