The Spireites controlled the game and deserved their first home victory over the Shrimps, who did not test goalkeeper Tommy Lee in the 90 minutes.
Chesterfield made Ritchie Humphreys captain on his 700th career appearance and the hosts marked the occasion by taking the lead in the 19th minute when Eoin Doyle crossed from the right and O'Shea headed in from eight yards.
Doyle had a chance to double the lead just after the break as Mason Bennett played him in but ex-Chesterfield goalkeeper Barry Roche saved at his near post, and he denied the striker again before the hour when O'Shea put him through.
The visitors had not threatened but Kevin Ellison gave the home side a scare when he shot just wide from 25 yards in the 74th minute while Sam Morsy rattled the Morecambe crossbar five minutes later.
- Sports & Recreation
- Eoin Doyle