ScotRail now won't hit its punctuality target until 2022
The operator had expected to reach 92.5 per cent of trains on time by March 2021 - but this is not now expected until March 2022.
It still presents a significant challenge since current performance, measured over the last year, is nearly 5 percentage points adrift at 87.6 per cent.
The punctuality figure has improved by only 0.3 points since January and the 92.5 per cent target was last reached six years ago, albeit with fewer trains on the network.
The target has now been put back from 2021 by the need for track improvements by Network Rail Scotland to cut hold-ups.
However, Mr Matheson told the Scottish Parliament's connectivity committee: "They are implementing the provisions within the Donovan review, and that set a trajectory of when they thought they would get to 92.5.
"What subsequently happened is that in looking at the further works that Network Rail need to take forward on infrastructure, the ORR [Office of Rail and Road regulator] have said they don't believe that ScotRail will be able to reach that target for at least a further year.
"What we now need to do is see what further measures can be taken forward to try and accelerate that."
The ORR told The Scotsman there were unofficial interim targets of 90.5 per cent by next March and 91.5 per cent by March 2021.
However, it agreed such a rapid improvement would be greater than had been achieved on Scotland's railways for years.
ScotRail later stressed that even the 2022 date was not wholly within the control of it and alliance partners Network Rail Scotland because delays could also be caused by trespassers, suicides, extreme weather, and other trains.
It said the March 2022 date was part of its current remedial plan, ordered by ministers this year because of poor performance on trains into Edinburgh.
ScotRail said: "This is the trajectory set by the Office of Rail and Road [regulator] because of the work it believes Network Rail has to undertake to achieve the 92.5 per cent target."
It said 11 of the 19 improvements in the plan had been made so far, including the lease of three additional diesel inter-city trains; an extra £500,000 a year for a performance improvement fund, and recruiting eight additional Hitachi technicians for its brand new electric fleet.
A ScotRail spokesperson said: “The successful delivery of our remedial plan remains a priority for everyone at ScotRail.
"We have made good progress implementing the plan, which is helping to deliver a more punctual and reliable service for our customers.
“We know we still have much to do to regain the trust of our customers, but the unprecedented investment we are making is already paying off, delivering more seats, more services and faster journeys across the country.”