"Not big but really slow" is an old joke shared in professional sports by those having a difficult time explaining the success of a particular athlete. There are times, the adage implies, when the whole greatly exceeds the sum of the (flawed) parts.

Barclays looks to be careening towards that rather hard-to-define vertex in the minds of investors and regulators as its flawed parts are, at the moment, outperforming on the sum basis, with shares having risen more than 50 percent since the bank's initial retreat from the Bob Diamond era earlier this summer.

However, new CEO Anthony Jenkins now faces an immensely complicated challenge as he attempts to both rebuild trust for the bank amongst his clients, shareholders and regulators and also return it to consistent profitability. And Thursday's earnings figures might have made that task even more daunting.

Ignoring the headline quarterly loss of £47m - largely the result of a bizarre £1.1bn application of an accounting rule that penalises banks for their improved fortunes - Barclays had a fairly decent quarter. Yes, it set aside another £700m to compensate customers for its role in the mis-selling of payment protection insurance and its return on equity measure slipped below 9 percent, but a powerful set of figures from the investment banking unit somewhat mitigated their impact on the bank's bottom line.

And it's there where Jenkins's chief dilemma lies: should he take advantage of the smaller global investment bank playing field to beef up earnings, or steer the lender out of the Diamond era with a deeper focus on retail banking and the sober image and mundane profits that come with it?

Challenging Options

Neither appears attractive at this stage.

Option A - ramping up investment banking - has the most initial temptation. The group's Fixed Income, Currencies and Commodities unit, known as FICC, posted a 29 percent jump in third-quarter profits despite an increase in revenues for the division of only 10 percent. Collectively, the workhorse investment banking division of Barclays, now run by former Diamond ally Rich Ricci, stoked £2.63bn into Barclays' global furnace.

FICC's performance paralleled huge gains across the world's ten biggest investment banking units, which collectively generated around $22bn in revenues for the three months ending in September, according to data compiled by Bloomberg.

But it's clear that an enormous portion of that gain can be linked to two - and perhaps four - key central bank decisions: ECB President Mario Draghi's promise to buy an unlimited amount of bonds in the open market to stabilize the borrowing costs of indebted Eurozone members and the extension of the Federal Reserve's multi-trillion programme of quantitative easing by Chairman Ben Bernanke.

Similarly fixed-income friendly moves from the Bank of England and the Bank of Japan have also added rocket fuel to the earnings potential of investment units with scale and capital.

All four decisions have driven a wave of bond sales - both sovereign and corporate - as borrowers rushed to get funding before the newly opened windows are slammed shut in a global economic slowdown next year.

Option B - building brand trust around a safe, reliable and sober retail banking model - looks increasingly difficult. Barclays was forced to announce yet another series of probes into potentially shady business practices in the United States just 24 hours after it earned the ignominious distinction of being the first British lender to face an accuser in court over the alleged mis-selling of financial derivatives to a business which manages care for the elderly.

Managing the media impact of having to set aside more than £2bn to re-pay customers who were urged to buy insurance products they didn't need is one thing. Doing the same with headlines that allege cheating a small business dedicated to taking care of the frail and infirmed is quite another.

Add in new allegations of potentially corrupt practices in the United States and both become next to impossible - especially when your bank's name is still the principal association to a global Libor rate fixing scandal thanks to your predecessor's decision to gain "first mover" advantage by cutting a deal with US and UK watchdogs.

Changes Ahead

So what to do?

Both industries are facing enormous changes: Britain's plans to hive-off retail banking from investment activities will severely hamper earnings potential in a "universal" banking model that relies on product cross-selling and multi-national economies of scale. Global regulatory demands for stronger capital buffers at investment banks will mute bank balance sheets, slow lending and sap profits.

Growing a retail business in the current toxic environment for "big" bank brands is tough, and seemingly reflected in the tiny year-on-year increase (£600m) in the bank's UK deposit base. Retail profits fell 5 percent on a nine-month basis to £1.4bn and UK retail banking pre-tax income fell 3 percent from the previous quarter.

Growing investment banking earnings might have gotten a tad easier, however, thanks to the effective withdrawal from the global fixed income markets by former underwriting leader UBS. Barclays is already firmly capitalised (its so-called core tier one capital ratio, a measure of the size of the buffer it needs to absorb potential losses, is around 11.2 percent and stronger than US rival Citigroup) and appears to be managing its cost base (its net operating income ratio fell to 64 percent from 68 percent last year).

However, the sugar-rush of deals sparked by Draghi and Bernanke and unlikely to be repeated in the coming quarters and a global economic slowdown will trim earnings potential in both domestic and international markets.

Jenkins did his best to manage reputational risk during his first investor presentation at CEO, assuring shareholders that Libor-riggers had been sacked and that efforts were underway to claw back any bonuses they had been paid and vowing to reduce overall compensation in the unit as a proportion of revenues.

But ultimately his tenure will be judged on performance, not perception.

This alone may be the reason he may find relying on investment banking earnings, even if they're "not big", a more attractive option than betting his future on the "really slow" growth in retail.