A second chance at Football League level materialised for McKellar in 1978, in the form of a £2,500 move to First Division club Derby County on 8 April 1978.
[11] He played around half the Rams' games during the 1979–80 season, making 26 appearances and keeping 10 clean sheets,[11] but the campaign ended with relegation to Second Division.
[10] He quickly staunched the flow of goals into the Bees' net and made 42 appearances during the 1980–81 season, which included a run of six successive clean sheets in December 1980 through to January 1981.
McKellar returned to England to sign for Second Division club Carlisle United in August 1983 for £4,000 in a part-exchange deal which saw Trevor Swinburne move to Brentford.
[2] McKellar moved to Edinburgh to join Scottish League Premier Division club Hibernian on a two-year contract for an £8,000 fee in 1985.
[15] Signed as backup for Alan Rough, the move reunited McKellar with Hibs assistant manager Tommy Craig, a former teammate at Carlisle United.
[15] After playing a few reserve team matches, McKellar walked out on Hibernian and accused the club of not paying his travel or accommodation expenses.
[2] McKellar signed for newly promoted Scottish League Premier Division club Hamilton Academical prior to the beginning of the 1986–87 season.
[17] Unable to keep Rikki Ferguson out of the team on a regular basis, McKellar made 16 appearances in the First Division prior to departing Douglas Park in early 1988.
[19] After failing to make an appearance in the early part of the 1988–89 season and spending time on loan at Fourth Division club Hartlepool United,[6] McKellar departed East End Park in October 1988.
[22] McKellar moved back up to the Scottish League Premier Division to sign for Walter Smith's Rangers in 1991, as backup for Andy Goram.