The NFL alarm clock goes off at 4 p.m. Tuesday afternoon, signaling the end of a prolonged silence and the onset of what is expected to be an interesting 2013 NFL free-agent signing period.

The Indianapolis Colts can begin investing a portion of their sizable salary-cap space for a pass rusher to replace Dwight Freeney, an offensive tackle to play opposite Anthony Castonzo and perhaps a guard to reinforce the interior of Andrew Luck’s protection.

General manager Ryan Grigson might also need to find a replacement for starting cornerback Jerraud Powers, whose contract expires Tuesday.

The Colts’ attempts at re-signing their 2009 third-round draft pick had been unsuccessful as of late Monday and indications are Powers will hit the open market.

“They definitely want him back,’’ said Cliff LaBoy, Powers’ agent. “I think they’re just playing it safe to see what the market is.’’

Grigson has been unavailable for comment, and LaBoy wouldn’t elaborate on what it would take for the Colts to retain Powers.

However, it’s believed the Colts consider Vontae Davis their No. 1 cornerback and Powers No. 2. That likely is reflected in the team’s offer.

LaBoy said other teams have shown interest in Powers. All it takes is one suitor to offer a contract that dwarfs whatever the Colts’ are offering.