Paceman Archer is in line to make a much-anticipated Test debut as a replacement in the XI for England's record wicket-taker James Anderson, ruled out at the Home of Cricket because of a calf injury that restricted him to four overs in the Specsavers series opener.
Leach, man of the match in his most recent Test outing against Ireland a fortnight ago, has come in for fellow spinner Moeen, who has been omitted after a poor showing in the 251-run defeat to Australia last week.
Moeen offered neither control nor a consistent threat in Australia's second innings, with unflattering figures of two for 130 from 29 overs containing two 'moon ball' beamers.
His ineffectiveness came under scrutiny after fellow off-spinner Nathan Lyon took six for 49 which helped to lift Australia into a 1-0 lead in the five-Test series.
The all-rounder also contributed just four runs with the bat and his recent run of low scores has seen his average dip below 30, prompting England to turn to Leach, whose improbable 92 as a nightwatchman ushered Joe Root's side to victory against Ireland.
Furthermore, Leach's slow left-armers are viewed as a potential antidote to Australia talisman Steve Smith, who averages 34.9 against orthodox left-arm finger spin, comfortably his lowest among the various modes of bowling.
Smith became only the fifth Australian to register hundreds in either innings of an Ashes contest at Edgbaston though England are likely to have more of a varied bowling attack at HQ.
Archer, England's leading wicket-taker during their triumphant World Cup campaign, is set to provide the pace threat, with the Bajan-born speedster capable of regularly bowling in excess of 90mph.
He was omitted in Birmingham due to concerns over a side strain but has proven his fitness in a Sussex Second XI fixture this week, taking six for 27 before amassing a breezy century against Gloucestershire's second string.
Fellow paceman Olly Stone's back injury precludes his involvement though left-arm seamer Sam Curran retains his place in the squad, as does Joe Denly, whose spot came under scrutiny after scores of 18 and 11 last week.
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