[8][9] Later that season, he won his first honours with the club, playing at loose forward in Castleford's 8–5 victory over Leigh in the 1967 BBC2 Floodlit Trophy Final at Headingley, Leeds on Tuesday 16 January 1968.

During the 1968–69 season, Reilly played loose forward in Castleford's 11–22 defeat by Leeds in the 1968–69 Yorkshire Cup Final at Belle Vue, Wakefield, on Saturday 19 October 1968, and played loose forward, and won the Lance Todd Trophy in Castleford’s 11–6 victory over Salford in the 1968–69 Challenge Cup final at Wembley Stadium, London on Saturday 17 May 1969.

[10] In the 1969–70 season, Reilly played loose forward in the 7–2 victory over Wigan in the 1969–70 Challenge Cup Final at Wembley Stadium, London on Saturday 9 May 1970.

[13] Early in the 1973 Grand Final against the Cronulla-Sutherland Sharks (playing their first Grand Final), a team which was captain-coached by Reilly's former Great Britain team mate Tommy Bishop, and also included former Lions prop Cliff Watson, Reilly was felled late by Sharks hooker Ron "Rocky" Turner after putting in a mid-field chip kick (Turner had already targeted him once and just missed him only a minute into the game).

As it was clear he would not last out the match, Manly coach Ron Willey gave the Englishman the instructions to go out and cause as much physical damage to the Sharks players as he could before he could go no further.

The game has often been described as the roughest, dirtiest Grand Final in Sydney premiership history, with several all-in brawls (usually started by Bishop before retreating behind his pack) causing referee Keith Page to caution both teams repeatedly, though strangely he did not send anyone from the field despite repeated warnings that he would do so (according to Bishop, at one stage Keith Page allegedly threatened to take Manly second rower Peter Peters out the back of the Sydney Cricket Ground after the game and 'sort him out' for calling him a cheat).

Leading journalist Ian Heads described the match in the Sunday Telegraph the next day as: "It was a Grand Final as tough and dirty as any bar-room brawl".

[14] 40 Years after that Grand Final, Sharks coach Tommy Bishop admitted that they did in fact target Reilly, knowing just how dangerous a player he was.

Bishop also lamented the fact that while his game preparation focused on targeting his former International team mate, he somehow managed to forget about the danger that was Bob Fulton.

Second rower Phil Lowe, and lock forward Steve "Knocker" Norton who bore an uncanny resemblance to Reilly, as well as Castleford halfback Gary Stephens.

[16] During his time at Manly, Mal Reilly was team mates with players who themselves would go on to become legends of the game including Bob Fulton, Graham Eadie, Ray Branighan, Fred Jones, John O'Neill, Terry Randall, and legendary try scoring winger Ken Irvine.

Reilly was the coach in Castleford's 15-14 victory over Hull Kingston Rovers in the 1985–86 Challenge Cup Final during the 1985–86 season at Wembley Stadium, London on Saturday 3 May 1986, in front of a crowd of 82,134.

[19] In 1987 he succeeded Maurice Bamford as the Great Britain Lions' head coach and opened his reign as with six wins, four against France, and two over Papua New Guinea.

[20] The Lions win in the 2nd test in Auckland also assured them a place in the 1992 Rugby League World Cup final against Australia in October.

In a tense Final played in front of a then international rugby league record attendance of 73,631 fans, Australian débutante centre Steve Renouf scored the only try of the game to give the Aussies a hard fought 10–6 win after the Lions had led 6–4 at half time.

Reilly quit as Great Britain coach in early 1994 (his place was taken by former Lions captain Ellery Hanley who was still playing for Leeds at the time).