"could only manage" is a grammatically correct phrase and can be used in written English.
Example: Despite his best efforts, John could only manage a passing grade on the difficult exam.
Olympic champions Australia could only manage fifth.
By 2010 they could only manage 66% between them.
Film cameras in those days could only manage short takes and were prohibited in theaters.
That's a far cry from six years ago when it could only manage tenth place.
Hillary Clinton's candidacy stumbled in 2008 when she could only manage third place there.
Mr Thorpe won, while Mr Phelps could only manage bronze on that occasion.
Mr Tsvangirai could only manage 1,258,401, or 42%; three minor candidates scooped the remainder.
Over the next seven games, he could only manage one more.
Wawrinka put 69 percent of his returns in play while Dolgopolov could only manage 45 percent.
The best performer, Ohio's The Berry Company, could only manage a score of B minus.
In 1990, even Noir and Bouchet could only manage to parody their earlier work.
