(Paul Beaty / AP)

Earlier today, Manager Davey Johnson called any discussion of the Nationals trading for a starter in the wake of Ross Detwiler’s setback “premature.” But the Nationals, it seems, have already started casting a net for possible trades in the lead-up to the July 31 deadline.

The Nationals have kicked the tires on Cubs right-hander Matt Garza, one person familiar with the situation said. Talks between the teams have not progressed to the point of the Nationals offering the Cubs a formal proposal.

The Nationals have have shown interest in Garza in the past. Before the Rays traded him to the Cubs before the 2011 season, the Nationals expressed interest in dealing for the right-hander, a person familiar with the situation said. The interest, the person said, was not aggressive, but not insignificant.

Garza is one of the most sought-after starting pitchers on the trade market, and so their initial interest will not necessarily lead to a deal. But it does show a willingness, if not a desire, to augment their rotation for the stretch run as they chase the Atlanta Braves in the NL East.

Injuries have limited Garza to 57 1/3 innings this season, but when healthy he has been excellent. He is 4-1 with a 3.45 ERA with 52 strikeouts and 18 walks. In his past four starts, Garza has allowed three earned runs in 30 innings, striking out 28. His swing-and-miss arsenal includes a fastball that has averaged 92.7 mph this year.

Garza, 29, is eligible to become a free agent this winter. Under the new collective bargaining agreement, any team that trades for Garza would not receive a compensatory draft pick in the event he signed elsewhere.

The price to acquire Garza would be steep. The Baltimore Sun reported the Orioles had offered infielder Jonathan Schoop and pitcher Eduardo Rodriguez for Rodriguez. Both prospects ranked among the Top 100 in baseball coming into the season, according to ESPN’s Keith Law list.

The back of the Nationals’ rotation faces several questions at this juncture. Detwiler may miss his next start with lower back stiffness, an injury that tends to linger in pitchers. Rookie Taylor Jordan has pitched well in two starts, but it would be inherently risky to lean on a 24-year-old fresh from Class AA. Dan Haren will come off the disabled list early next week trying to recapture his old form — he went on the DL with shoulder inflammation with a 6.15 ERA.

Garza is widely expected to be traded before the deadline. The Cubs (36-48) entered Saturday 16 1/2 games out of first place in the NL Central and have already traded starting pitcher Scott Feldman to the Orioles.