Jonny Bairstow and Eoin Morgan shine for England in Mumbai

Bairstow (right) and Morgan shared a stand of 158 (AP)

Jonny Bairstow and Eoin Morgan proved all is well with England's back-up middle order - but the tourists are still none the wiser about the identity of Alastair Cook's new Test opening partner.

Another failure from Nick Compton and only a modicum of comparative success for Joe Root saw to it that more evidence is urgently required before either can be pencilled in for a debut as Andrew Strauss's replacement in the first Test against India.

Instead, by way of consolation but of less direct relevance to the grand plan perhaps, Bairstow (118) made his maiden first-class hundred in an England shirt.

He and Morgan (76) shared a stand of 158 to rescue England from 66 for four on the way to 338 for six on day one of three against Mumbai A at the Dr DY Patil Sports Stadium.

Compton this morning followed his duck against India A on Tuesday with just a single, while Root succumbed to the last ball before lunch for a painstaking 28 on debut.

His was the third wicket to fall for just 10 runs against Mumbai A, leaving Morgan and Bairstow - runless between them - with an important job to do to ensure England's innings did not fall well short of expectations against a routine attack on a fair pitch.

They performed admirably throughout a wicketless second session.

Morgan clubbed Suryakumar Yadav high over long-on for an early six in an 81-ball 50 also containing six fours.

Bairstow, scorer of 95 and 54 in England's most recent Test match at Lord's, may nonetheless soon find himself back in an understudy role again thanks to the 'reintegration' of Kevin Pietersen - the man he deputised for at HQ.

For good measure, he added a 158-ball century here, underpinned by sound shot selection and execution and completed with a flourish with a fierce cut for his 13th boundary off Kshemal Waingankar.

Even so, it was a fair bet Cook and coach Andy Flower would have readily swapped all of that for a more clear-cut indication of whether Root or Compton is likely to have what it takes in Ahmedabad on November 15.

The 'shoot-out' billed between them lasted little more than quarter-of-an-hour after stand-in captain Stuart Broad won the toss in a match minus the rested Pietersen.

The two contenders at least both got off the mark, Compton having to dive in to complete the scampered single which got Root under way.

His reward, however, was a good ball soon afterwards from Waingankar which held its line and evaded his forward-defence to knock out off-stump.

Root fared better, coming through the initial threat of Waingankar - a seamer who took five wickets against England four years ago when they were bowled out for just 98 in a crushing limited-overs defeat but who is playing in only his 12th first-class match at the age of 27.

The Yorkshireman, six years younger, displayed the maturity which has impressed so many as he waited more than an hour before registering a boundary - a clip off his legs when Shardul Thakur returned for his second spell.

It was to be Root's only four, before he was caught at short-leg off the part-time bowling of home captain Yadav on the stroke of lunch.

Jonathan Trott had shared a half-century stand with Root before a waft at a wide one from Javed Khan brought only an edge behind.

Ian Bell, also caught by wicketkeeper Sufiyan Shaikh when Waingankar found the edge with movement off the pitch, like Compton made his second single-figure score on tour - adding four here to the five he managed at the Brabourne Stadium.

But Bairstow and Morgan were up to the task, in a stand featuring just one minor moment of fortune in 40 overs when the wicketkeeper's mistimed push off the back foot did not stick in Waingankar's fingers on 56.

Thakur eventually had Morgan lbw with a yorker. But Samit Patel (59no) continued his fine form with another 50, in only 60 balls, to help Bairstow past his hundred in a near run-a-ball century partnership, which ended just before the close when the latter edged Javed low to first slip.