The accountancy software provider, a top holding for Citywire AAA-rated Terry Smith and AA-rated Nick Train, fell 5.5% to 629.4p as analyst Steve Goulden labelled the stock a 'sell' and cut his price target.
'Over the last few weeks, we have spoken to a number of accountants and resellers across the UK, US and Australia, along with senior figures from key competitors Xero and Intuit,' he said.
'Our key takeaway from these conversations is that the competitive situation in Sage's core mid-market franchise appears to be worsening.
'Entry level players at far lower price points are moving upmarket and are building functionality either internally or through third party platform partners. Higher end competitors also appear to be gradually gaining share from Sage's core user and reseller base.'
Sage is a major holding for Smith in his £16.2 billion Fundsmith Equity fund, although the stock no longer makes it into his top 10.
The shares meanwhile account for 5.1% of Train's £5.6 billion Lindsell Train UK Equity fund and 4.9% of his Finsbury Growth & Income trust.
The shares are down 21% since the turn of the year as
Train acknowledged in an update to investors last month that the company faced challenges 'in migrating its business to the cloud, in the face of new competition from exponents of the new cloud technology'.