Considered one of the best goalkeepers in the UK during the mid-1950s, Merrick was one in a long line of great Birmingham City keepers which included the likes of Johnny Schofield and Harry Hibbs.
This meant that Merrick had to wait until 20 May 1940 to make his debut in the Birmingham first team, then playing in the Midland Regional League because of the Second World War.
Merrick also played in the 1955–58 Inter-Cities Fairs Cup, in which Birmingham were knocked out at the semi-final stage by Barcelona, losing 2–1 in a replay at the St. Jakob Stadium in Basel.
He is perhaps best known for being the last line of defence against the Hungary side of Ferenc Puskás and Nándor Hidegkuti, the "Magnificent Magyars" who beat England 6–3 at Wembley in 1953 and 7–1 at the Nepstadion in 1954.
The 1960-61 tournament did produce a win for Birmingham at the San Siro against Internazionale in the semi-final; they were the only English team to achieve this for around 40 years.
Although Merrick spent well in the transfer market, bringing in such players as Jimmy Harris and Welshman Ken Leek, Blues failed to make much impact on the First Division, and finished 17th in the 1961–62 season.
By far the best achievement in Merrick's reign at the club came in the 1962–63 season, when he successfully led the Blues to the League Cup title, beating Aston Villa in the final[1] thanks to goals from Ken Leek (2) and Jimmy Bloomfield.
At the end of the 1963–64 season, in which Birmingham City again failed to make much impact in the league and finished 20th, the club requested Merrick's resignation.