Lampard kept faith in Tomori despite his horror show against Leeds, but the defender made another error the following week as Derby were beaten at Millwall; he pointlessly stuck out his leg to block a Shaun Williams shot, inadvertently sending it flying past Scott Carson in the Derby goal. As soon as Dalsgaard got in front of Tomori, the latter was never going to win the header Mount is expected to introduce himself on the world stage with an impressive performance at Old Trafford Since losing at Millwall, Derby have tasted defeat in just one of six league games, with Tomori playing every minute at the heart of a defence which has conceded only three goals – keeping three clean sheets in the process. With Carabao Cup matches included, Tomori has helped the Rams keep five clean sheets in 10 outings – a remarkably impressive return.He ranks highly among his rival Championship central defenders for completed defensive actions, and while people may point at an average tackle rate of 2.3 per game as being far too high for a centre-back, Tomori is a reactive defender who is playing as part of a high-line. Carabao Cup commentaries LIVE on talkSPORT Mason Mount has been living up to expectations since joining Derby on loan earlier this year, finding the back of the net five times in just 11 games.The England youth international excelled for Vitesse last season to be named their Player of the Year, and though there were calls for the 19-year-old to be sent on loan to a Premier League side, Championship outfit Derby won the race to capture the talented teenager. 5 Heading remains a weakness for the 20-year-old, with his aerial duel win rate below 50 per cent for the season, and he was caught out again on Saturday as Derby came from behind to beat Brentford. Henrik Dalsgaard scored for the Londoners inside the first minute by beating Tomori to a corner and heading home; it was an easy header for Dalsgaard to win, as Tomori failed to react to his movement and was nowhere near the ball as it was delivered into the area. 5 Manchester United vs Derby (Tuesday, September 25) – LISTEN LIVEOxford United vs Manchester City (Tuesday, September 25) – LISTEN LIVELiverpool vs Chelsea (Wednesday, September 26) – LISTEN LIVETottenham vs Watford (Wednesday, September 26) – LISTEN LIVE 5 Tomori was caught too deep (left), lost his man (centre), and failed to make amends with an attempted block (right) 5 5 Tomori starts getting back after Chelsea’s defence is breached (left), he wins the tackle (centre), and starts building play from the back (right) Their ability to sign Mount was considered to be largely down to Frank Lampard, the Chelsea legend, who was appointed Derby manager over the summer.And it appears Mount is benefiting from playing under a manager who was himself a prolific goal scoring midfielder, with the teenager leading Derby’s scoring charts at this early stage of the campaign.Mount’s scoring feats have claimed all the headlines, understandably so, but his form has stolen the limelight from the other player who joined him in swapping Stamford Bridge for Pride Park over the summer.Fikayo Tomori penned a season-long loan deal with Derby about three weeks after Mount did, and he’s started every single game since joining the Rams.Tomori, the defender, looked shaky in his opening appearances; his debut was a 4-1 defeat to Leeds in which he was at least partially at fault for three of the goals scored by Marcelo Bielsa’s side.The 20-year-old’s most glaring weakness to show up against Leeds was an almost comical inability to head the ball. Two of Leeds’ goals came from Tomori missing headers, while the third was a result of the youngster sitting off his man on the edge of the box, allowing him loads of space to run into. Jody Morris, the Derby assistant manager, has suggested these errors were down to concentration rather than any lack of ability on Tomori’s part.“He has had some outstanding games for us but he has also had some games where his concentration levels could have been a little bit better,” Morris said. “That is not me digging him out, it is me realising he has the capabilities to perform at the levels he has shown in a few of the games, more often.”Given the Leeds and Millwall defeats were Tomori’s first appearances in a new team, he can be forgiven for such errors, and the turnaround since then is clear to see. Derby are Tomori’s third loan club, after Brighton and Hull Tomori will face his toughest test on Tuesday evening as Derby travel to Old Trafford to take on Manchester United in the Carabao Cup – LIVE on talkSPORT.With Marcus Rashford suspended for the hosts, Jose Mourinho is expected to field first-choice forward Romelu Lukaku up front, meaning Tomori will come up against one of the most well-rounded strikers in world football.Lukaku’s ability to combine excellent technical ability with his physical strengths often see him bully defenders with ease, and Tomori will know this is the perfect audition to earning a future Chelsea career.Manchester United vs Derby County is LIVE on talkSPORT. Click here for team news and live commentary streamThe Blues come up against strikers of Lukaku’s quality on a consistent basis, and if Tomori can handle Lukaku in a one-off game, there is no reason to say he could not do it week in, week out.Lampard is expected to name his strongest line-up to start at Old Trafford, meaning both Mount and Tomori will take to the field from the beginning. All eyes will be on Mount – tipped to be a future star for both Chelsea and England – but this is the kind of match in which Tomori should be the focus, as he could prove his unheralded excellent start to the season is not just a period of good form, it is normality.