The Rockies will not trade right-hander Ubaldo Jimenez unless it is a perfect fit. The Reds, a team capable of putting together such a match, have Jimenez on their radar, major-league sources say.

Yet, the Reds are not certain buyers.

The team, while only four games out in the NL Central, is in fourth place. If the Reds continue to under-achieve and fall further behind in the next two weeks, they could become sellers, sources say.

Closer Francisco Cordero and catcher Ramon Hernandez, both potential free agents, would be pieces the Reds could try to move. Cordero, though, has a limited no-trade clause, and can block deals to certain clubs.

Even if the Reds are buyers, they might be limited in the salaries they could add. Their average attendance this season has only improved from 25,348 to 26,730, an increase of just 1,382 per game. The club, coming off its first NL Central title since 1995, surely hoped for a greater jump.

Jimenez, 27, could fit both the Reds’ rotation and their budget.

The Rockies, according to one source, have yet to engage in meaningful dialogue about Jimenez with the Reds or any other club. But the Reds, 14^th in the National League in rotation ERA, are looking for ways to upgrade both their starting and relief pitching.

Jimenez, after a rocky start this season, has produced a 2.52 ERA in his last eight starts. His contract, meanwhile, is decidedly club-friendly. He is signed for $2.8 million in 2011 and $4.2 million in ‘12 with club options of $5.75 million and $8 million in ‘13 and ’14.

The Rockies would weaken their starting pitching considerably if they traded Jimenez, and his bargain salaries will only add to the team’s asking price in a trade.

The Reds, though, could meet that price by starting a package with a young pitcher such as right-hander Homer Bailey, righty Mike Leake or Class AAA lefty Travis Wood. The team also is deep in young hitters at a variety of positions.

-Ken Rosenthal and Jon Paul Morosi